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EASI User's Guide V90.book

1. execute the LUT task RUN LUT EASI User s Guide 37 The Entire ENHANCE EAS Script 38 PCI Geomatics EASI Programming Overview In addition to being a command environment for interactively executing tasks EASI is also a full featured interpreted programming language EASI supports control structures such is FOR WHILE and IF statements the definition of variables and structures the definition of functions taking any number of arguments and providing a return value and a powerful set of built in intrinsic functions EASI can be used to develop specialized and powerful applications Scripts Functions and Intrinsics Like the simple scripts introduced in the previous section EASI programs are stored in text files with upper case names ending with the extension EAS These files may be created with any text editor In fact there is no difference between the EASI scripts from the previous section and the more powerful programs described here except that these programs draw upon the full set of EASI commands EASI User s Guide 39 Scripts Functions and Intrinsics It is possible for an EASI script to call another EASI script providing subroutine type capability and for an EASI script to call itself providing recursion However EASI scripts are limited in that there is no direct way to pass data to them nor for them to return a value except through setting EASI parameters and manip
2. 7 1 2 1 2 ENDMODEL If channel 7 is 8 bit some scaling and adjustment is necessary MODEL ON irvine pix OVER dbiw 7 1 2 1 2 128 127 5 ENDMODEL Create a bitmap mask segment 2 which is true 1 everywhere channels 1 and 2 are less than 25 Then this mask and the mask EASI User s Guide 103 Data Modelling in segment 3 are used to determine a region that should be zeroed in image channels and 2 if 1 lt 25 and 2 lt 25 then 2 1 else 2 0 endif if 2 1 and 3 0 then LUT The following example reads an LUT using DBReadLUT and Example then applies it to an image channel using a MODEL expression local byte lut 256 integer fd fd DBOpen pci demo irvine pix w call DBReadLUTC fd 2 lut 1 lut 1 1 call DBCloseC fd History Perform a ratioing of two channels into a third Before starting Records an abort message is set and if the operation succeeds a descriptive history record is written fd DBOpen file r call DBwriteHistory fd IMG 3 fd 3 fd 2 fd 1 1 call DBWriteHistory fd IMG 3 Ratio of Channels 1 and 2 call DBClose fd 104 PCI Geomatics Error Handling Overview The execution of tasks intrinsic scripts and user functions can cause an error to occur as can even the execution of a simple statement Every EASI error is identified by a numeric error code and
3. DEBUG ENABLE 3 The DEBUG LIST command is used to list all the current breakpoints the source files and names of the associated functions the line numbers at which they are set and whether they are enabled or disabled DEBUG LIST The DEBUG STEP command is used to execute the next line of code DEBUG STEP DEBUG STEP OVER EASI User s Guide 153 Commands Quit If the additional modifier OVER is given to the DEBUG STEP command then execution will not stop inside called functions Otherwise when stepping at a function call execution will halt at the first line of the called function When stepping past the end of the current function the execution will halt at the next line of the calling function The DEBUG QUIT command is used to return from the DEBUG prompt immediately to the main EASI prompt without executing any further statements DEBUG QUIT DELETE The DELETE command deletes the named file assuming the user has permission to do so The ONERROR statement is invoked if the delete fails A NOERROR clause may be used instead to suppress any errors DEL ETE filename ONERROR statement filename a string expression for the filename to delete Example The following example converts a TIFF file to a PCIDSK file and then deletes the TIFF file using the DELETE command fili irvine tif filo irvine pix run fimport delete fili noerror 154 PCI Geomatics Chapter 8 EASI Language
4. DOC 2 SECOND DOC These two lines are associated with subtopic SECOND DOC which is itself a subtopic of FIRST DOC 3 THIRD DOC This is a subtopic of SECOND DOC 3 FOURTH DOC This is another subtopic of SECOND DOC 1 FIFTH DOC This is another first level subtopic like FIRST DOC but this topic has no subtopics of its own 32 PCI Geomatics Chapter 3 Developing Simple Scripts Example Documenting ENHANCE EAS The DOC statement can be used to add on line documentation to the ENHANCE script Such documentation could include a general description of the function of the script specification of its input parameters and or an example of its use DOC DOC ENHANCE DOC DOC Given an input file and channel number create a new boc file containing a 512x512 sized copy of the input with DOC equalization enhancement applied DOC DOC 1 PARAMETERS DOC DOC ENHANCE requires the following input parameters DOC DOC Name Prompt Count Type DOC DOC INFILE Name of input file to be processed 1 64 Char DOC DBIC Database Input File Name 0 1 Int DOC OUTFILE Name of output file to be created 1 64 Char DOC DOC 2 INFILE DOC DOC The name of the input file from which data will be enhanced DOC DOC 2 DBIC DOC DOC The channel within the input file which is to be enhanced DOC DOC 2 OUTFILE DOC DOC The new file to create which will be of size 512x512 and contain DOC a single channel with the e
5. EASI gt print ListoOfNames Alexander Betty Charles Note that it is not possible to insert a string into the middle of an MSTRING nor to delete a string from an MSTRING There is no automatic reshuffling of indices The third special type available in EASI is the MVAR which is a modelling intermediate array Further discussion on this variable and on modelling in general is deferred to a later chapter Variables of these special types are declared in the same manner as the basic types using the LOCAL or GLOBAL statements Note however that it is not legal to declare arrays of type STRING MSTRING or MVAR nor to declare pointers to these variables Structures It is possible to build aggregate variables in EASI by defining and using structures A structure is composed of any number of basic variables strings mstrings and other structures associated together into a single unit Once defined a structure EASI User s Guide 47 EASI Variables is equivalent to a new variable type available to EASI Variables of this new type can be declared using LOCAL and GLOBAL statements just like other variables Structures are defined using the DEFINE command Since a single structure definition consists of may lines structures are not defined interactively at the EASI prompt but normally only in EASI procedures An example of a simple structure definition is DEFINE STRUCTURE Point DOUBLE X DOUBLE Y ENDDEFINE The
6. On a standard video terminal the screen has 24 lines of 80 columns 132 columns on advanced terminals The print statement can move the cursor to any of these positions using EASI User s Guide 173 Commands the format expression The upper left corner is column 1 row 1 Once the cursor has been moved all subsequent output will be after that position This allows a user to place output anywhere on the screen At the end of a print statement the cursor is moved to the first column of the next line CLREOS CLREOS and CLREOL are format expression subcommands andCLREOL which clear portions of the terminal screen quickly CLREOS clears the screen from the current cursor position to the end of the screen Note that on some terminals this command always clears the entire screen CLREOL clears from the current cursor position to the end of the current line Examples PRINT 1 1 CLREOS clear the whole screen PRINT 10 5 CLREOL clear line 5 from column 10 to the end of the line BOLD The following format subcommands assign attributes to BLINK characters being printed in order to highlight text and diagrams REVERSE f UNDER BOLD Brightens printed characters ALLOFF BLINK Causes printed characters to blink on and off REVERSE Creates characters on a reverse background UNDER Underlines characters ALLOFF Switches off all active attributes Any combination of attributes can be used Example PRINT CREVERSE
7. character cannot be used to hold the cursor to allow subsequent output to start at the end of current output The character is only valid if followed by input i e an INPUT or ASK statement with no associated prompt Also note that INPUT and ASK have internal default error handling and reprompting which may yield unexpected cursor movement Example The two procedures shown below may not have the same effect since the prompt output by the INPUT statement always starts at the beginning of a new line 10 LOCAL A 20 PRINT 5 20 ENTER DATA 30 INPUT A 10 LOCAL A 20 PRINT 5 20 30 INPUT ENTER DATA A EASI User s Guide 177 Commands PRINTF The PRINTF command is an alternative to the PRINT command that allows format control in the spirit of the C function printf PRINTF format_specifier arg arg The format_specifier can be almost any legal printf format The argument expressions will be evaluated and the result output according to the format_specifier The format_specifier should consist of plain text interspersed with argument formats The argument formats consist of a percent sign followed by an argument type which may be one of d for integer s for string and f for floating point In actual fact almost the entire printf format syntax is supported but will not be described here Example PRINTF Hello s how is your day n myname Hello Frank how i
8. endfor call DBClose fd return buffer ONERROR if fd lt 0 then call DBClose fd endif if Cbuffer lt NULL then call EFree buffer endif call ReCastEASIError ENDONERROR ENDDEFINE The ONERROR block ensures the file is closed and that allocated memory is freed when any errors occur anywhere during the execution of the TRY block The error is then re cast at the end of the onerror block so that it can be detected by a higher level error handler Since the DBOpen function returns zero if an error occurs instead of causing an EASI error the EASIError intrinsic is used directly to trigger an error so that the error handling code can immediately take over The ReadChannel function could then be used as follows for example to compute the average value within an image channel local float ptr buffer local integer i local double sum average try buffer ReadChannel irvine pix 1 for i 1 to f len Cbuffer sum sum buffer i 114 PCI Geomatics Chapter 6 Error Handling endfor average sum f len buffer call EFree buffer onerror print The following error occured print GetLastErrorMessage endonerror Note that using EASI to perform a large computation such as in the above example is not particularly efficient and could take a relatively long time for even moderately sized images EASI User s Guide 115 Trapping Errors in Blocks of Code 116 PCI Geomatics O
9. 8 and 9 if Cmod geox 1000 lt sizex or cmonegcoy s 1000 lt sizey then 8 Se 9 255 else 7 1 8 2 9 3 endif The following model prompts the user for the spacing in pixels for a regular grid as well as an input and output channel local int spacing in_chan out_chan input Enter the grid spacing spacing input Enter the input channel in_chan input Enter the output channel out_chan 102 PCI Geomatics Chapter 5 Working with Data Test Image Example Blending Example Arithmetic Example Bitmap Example if Cmod x spacing 0 or Cmod y spacing 0 then f out_ chan 255 else f out_chan in_chan endif Create a grey level ramp of 0 to 255 across an image plane model on filo 7 x 1 255 dbx endmodel Create an image which smoothly blends channel into channel 2 as we move across the image The output is placed in channel 7 In this case we want to operate on the whole default database The default database in this case is implied by the FILE parameter The MODEL command does not have to be explicitly listed as itis implied by the channel variable in the equation FILE irvine 7 0x Dao i dbx x dbx 1 Perform a Vegetative Index calculation using channels and 2 saving the result to channel 7 If channel 7 is 32 bit real the following model is used MODEL ON irvine pix OVER dbiw
10. AND this access lt gt r then call EASIError 702 Invalid access for operation endi 134 PCI Geomatics Chapter 7 Object Oriented Programming With EASI local integer fieldnum fieldnum FindSubString this fieldnames field if Cfieldnum 1 OR Ff len field f lenCthis fieldnames fieldnum then call EASIError 701 Field s not found field endif call vecSetField this fd this layer this shape fieldnum value enddefine The dynamic field access methods make it particularly convenient if a script is written for vector layers with a known set of attribute names For example the following script can be used to iterate over all the shapes in a layer and print the attributes called Attribute and Group for each shape to the screen local VLShape shape call shape open irvine pix 25 call shape FirstQ while shape AtEnd TRUE printf Attribute s n shape Attribute printf Group s n shape Group call shape Next endwhi le call shape close EASI User s Guide 135 A Sample Class 136 PCI Geomatics EASI Language Reference Commands EASI is a command language tailored for the launching of PACE programs and raster modelling This chapter contains an extensive list of EASI Commands ALIAS The ALIAS command is used to create and maintain command line aliases which can cut down on typing and will allow for the con
11. THIS WILL BE HIGHLIGHTED CALLOFF 174 PCI Geomatics Chapter 8 EASI Language Reference Note Not all attributes are supported on all terminals Previously selected terminal options e g cursor type may affect the attributes If an attribute is not supported on the selected terminal it will have no effect RFIELD By default numeric values are printed in fields eight characters wide The RFIELD subcommand allows you to specify a field width of 1 to 40 characters This is useful for formatting output or allowing a larger field for more significant digits The numeric field width is set back to the default of eight after the PRINT statement completes The form of the subcommand is CRFIELD numexpr where numexpr is a numeric expression with a value from 0 to 40 AN Note If RFIELD is set to 0 the field width will automatically be altered to exactly the width required by the printed numeric value Examples PRINT 1 2 3 yields 1 PRINT Cee eee yields ae CRFIELD 4 4 567 yields ner CRFIELD 0 1 2 5 1 yields 1 25 1 BOX The BOX expression is used to draw boxes on most terminal types it is ignored on other terminal types The form of this expression is EASI User s Guide 175 Commands BOXCLEAR PCILOGO BOX Cupperleftcol upperleftrow lowerrightcol lowerrightrow Example PRINT BOx 1 1 60 5 draws a rectangle with the upper left corner at column 1 row 1 and the
12. YOff XSize YSize format The modeling command _list can be any of a variety of commands The most important command that can be applied in a model is a modeling assignment This is a normal assignment LET statement using database channel specifiers for assigned to and source values If the window specification is not provided the entire source database area is operated on If no database name is provided the last database opened with DBOpen is used If no databases are open the FILE parameter is inspected and used If this database cannot be opened the MODEL command will fail It is also possible to enter modeling assignment operations without the MODEL ENDMODEL command in some cases Any assignment statement for which the assigned to value is a channel will be considered an implicit model and the usual rules for a default database of operation will apply For example the following commands will set all of channel 8 of irvine pix to zero in a manner similar to the CLR PACE task FILE irvine pix EASI User s Guide 169 Commands Arithmetic Example Blending Example Test Image Example 8 0 Modeling can be used for both imagery and raster GIS applications The examples presented here have been selected to show a range of possible applications and to stir the user s imagination See Also Modeling Expressions Perform a Vegetative Index calculation using ch
13. max and defaults SEE parm DEFINE parm one to eight character identifier Example SEE dbiw DEFINE SHOW The SHOW command shows the current parameter values within a specified range SHOW parm max min parm name of parameter file entry max maximum number of values to show min minimum number of values to show Min defaults to 0 if not specified max defaults to the number of values in the parameter STATUS The STATUS command shows all parameters and their current values used in controlling a procedure or PACE task Is is primarily used interactively S TATUS task task the name of an EAST procedure or PACE task 180 PCI Geomatics Chapter 8 EASI Language Reference STATUS_SHOW The STATUS SHOW command displays parameters when a procedure is statused STATUS_SHOW parm max min parm name of a parameter max maximum number of data values required expression min minimum number of data values required expression This command is placed within EASI procedures to define the parameters the procedure expects When a STATUS command is used on a procedure a parameter is listed for each STATUS SHOW command Example In the following example the DBIC parameter is displayed If there are more or less than three values assigned to the parameter a warning will be generated status_show dbic 3 3 See Also STATUS_ TITLE STATUS STATUS_TITLE The STATUS_TITLE com
14. satisfied it will appear that the debugger is stopping twice on the same line Actually the second time it stops on that line corresponds to executing the statement associated with the IF If you type QUIT or BYE or EXIT from the DEBUG prompt execution of the script will continue until it terminates after which EASI will itself terminate Since the DEBUG family of commands are somewhat long to enter it is convenient to define aliases to abbreviate these commands The following is a reasonable set of aliases to use al i as dbl DEBUG LIST alias dbb DEBUG BREAK alias dbs DEBUG STEP alias dbc DEBUG CONTINUE alias dbe DEBUG ENABLE alias dbd DEBUG DISABLE alias dbq DEBUG QUIT Aliases can be set in the easi startup file so that they may be automatically loaded each time EASI is run See Also STARTUP ALIAS The DEBUG BREAK command is used to set breakpoints A breakpoint is a special marker associated with a line of code that will cause execution to halt and a special interactive mode to be entered where variables can be examined from which execution can be allowed to continue DEBUG BREAK function name linenumber DEBUG BREAK file name linenumber DEBUG BREAK ONERROR Example Set a break point in function Test at line 5 DEBUG BREAK test 5 EASI User s Guide 151 Commands Clear Continue Set a break point in file TEST EAS at line 5 DEBUG BREAK TEST EAS 5 The function in
15. Corporation Microsoft is a registered trademark and Windows is a trademark of Microsoft Corporation MrSID is a registered trademark of LizardTech Inc Copyright 1995 2003 LizardTech Inc All rights reserved UNIX is a registered trademark of The Open Group Copyright c 2002 Mapping Science Inc GeoJP2 is a trademark of Mapping Science Inc The GeoJP2 format is the intellectual property of Mapping Science Inc All other trademarks and registered trademarks are the property of their respective owners Table of Contents Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Introduction Purpose Of EAS cccccccccssssesessseceeeeceeceeeeceeeeeeeeeseeaeaeaesuaeaaeasasesens 1 Using EASI Overview of Using EASI ccccecceeeeeeeetteeeeeeeecieeeeeeteeeeeeeiaeeeeeenee 5 Getting Help HELP 0 c cccceeceseeccceeeeeeneceeeseneceeeeeeeneneeenseeeceeeeeeens 8 Parameters sis eaigiae eanstsnehsdearvons heist T eee 9 Setting and Changing Parameters Variables LET 0 11 Displaying Parameters PRINT cceceesseeeeeeeeeeeneeeeeeeeneeeeeeeeaas 12 Examining Parameter Sets STATUS 13 Searching For Parameter Names SEE 14 Running Procedures RUN ccceeesceeeeeeeeceeeeeeeeeneeeeeeeneeeeeeneaas 14 Keeping a Record of Your Work LOG eeceeceeeeeeeeeeeeeettteeeeeeenee 15 When You Are Finished ccccccceeeseeeeeeeeneeeeeeeenaaeeeeeeenaaeeeeeeeaaes 18 SOMMA E a
16. EASI provides a simple and convenient mechanism for querying and setting input parameters required by an executable module referred to as a task The interactive user is able to view a complete list of all the parameters required as input by a task check their current values modify their values and execute the task As a scripting language EASI can be used to automate those manual procedures that are performed by a user interactively A set of commands can be placed in an ordinary text file called an EASI script to specify parameter values and execute tasks Chains of such commands in an EASI script can be used to EASI User s Guide Purpose of EASI automatically compute more complex or time consuming results In addition to support for simple automation scripts the EASI scripting language includes a complete set of control structures with which complex applications can be built EASI also includes a rich set of intrinsic functions which permit the manipulation of data in a platform independent way Examples of data that can be accessed and manipulated include raster imagery vector data projection information and general binary and text files The EASI User s Guide The EASI user s guide describes in detail the interactive command and programming capabilities of EASI e Chapter 2 Using EAST focuses on the use of EASI as a command environment demonstrating how tasks can be executed and their inpu
17. Reports Procedure status reports are generated by the use of STATUS commands STATUS_END STATUS_ SHOW STATUS TITLE placed within a procedure In general a procedure would typically contain a STATUS_TITLE command to generate identification of the procedure followed by one or more STATUS_SHOW commands to show which parameters are required and a STATUS_END command to indicate the end of the STATUS commands While the STATUS commands can be anywhere in a procedure it is conventional to place them near the top When a status report is requested the procedure is searched line by line for STATUS commands All other commands are ignored In RUN or HELP mode STATUS commands are treated like REMark statements and have no effect Generating A Title STATUS_ TITLE The STATUS_TITLE command allows EASI to generate a header when you request the status of your procedure This header includes the date time software identification and a title description of up to 40 characters The form of this command is STATUS_TITLE string where string is a title description of 1 to 40 characters The STATUS_TITLE command must be the first STATUS command in a procedure If it is missing a default title is generated EASI User s Guide 29 SEEing Defaults of Parameters Showing Parameters STATUS_SHOW This command has the form STATUS_SHOW parm max min where parm is the name of a parameter max 1S a numeric con
18. Scope Rules With Examples EASI variables were designed to allow speed flexibility and above all modularity By declaring variables local the user is guaranteed that no other procedure has access to those variables Global variables however can be accessible to other procedures no accidental cross references can be made between the two types of variables The following give examples of variable interaction and scope rules Procedure xXx Procedure Y GLOBAL NUMERIC A B LOCAL NUMERIC B B 2 B 6 RUN Y RETURN PRINT A A B B EASI User s Guide 53 EASI Variables The result from running procedure X would be A 5 B 2 Procedure Y uses global A from procedure X thus the assignment A 5 in procedure Y assigns 5 to the global variable A However since procedure Y declares B to be local to procedure Y there is no connection between the local variable B in procedure Y and the global variable B in procedure X i e the fact that they have the same name is of no importance they are separate variables stored in separate memory locations One significant advantage for connecting values through the careful use of locally and globally declared variables is achieving greater modularity It becomes possible to connect collections of procedures together without having global variables in one procedure affected by the global variables used in a called procedure An string assignment variation on the above example wo
19. The object on which the method is invoked will be known as this within the method If the method is named Initialize then it will be used as a constructor for the class It will be automatically invoked each time an object of the class is created Normally the constructor is used to assign initial values to the class fields The Initialize method cannot take any arguments If the method is named Destroy then it will be used as a destructor for objects in the class It will be automatically invoked each time an object of the class is destroyed Normally the destructor is used to free any additional memory associated with the class Example Define a class called Circle with two initialization methods DEFINE CLASS Circle ReadOnly double centerx double Ccentery double Radius double Area EndReadonly EASI User s Guide 147 Commands Example ENDDEFINE DEFINE METHOD A itert x y ON Circle this centerx this Centery ENDDEFINE y DEFINE METHOD SetRadius new_radius ON Circle this Radius new_radius this Area 3 1415927 this Radius this Radius ENDDEFINE DEBUG The DEBUG command provides an interface to a set of command line debugging tools These include setting and manipulating breakpoints and single stepping through lines of code The various debugging commands are executed by entering DEBUG followed by additional key words and options The debugging commands are intended for in
20. a given string given the location and length of the substring to extract For example to extract a string starting from the 11 character of the string called data that is 10 characters long EASI gt print data filename irvine pix EASI gt print f extract data 11 10 irvine pix The Tokenize intrinsic function is used to break up a white space delimited string into an mstring White space is any number of spaces tabs and newline characters For example given a string called data that contains four numeric values EASI gt print data 3 5 7 9 5 5 EASI gt local mstring t EASI gt t Tokenize data EASI gt print t 3 5 7 9 5 5 The resulting mstring called t will have four lines each containing a substring from the input line with the white space removed The Tokenize function also takes an optional second argument specifying alternate delimiters For example EASI User s Guide 85 Database Files Database to separate a string by commas and spaces the following form of the Tokenize command could be used EASI gt print data 5 7 9 5 5 EASI gt t Tokenize data EASI gt print t 3 5 7 9 5 5 The f char and f ascii intrinsic functions can be used to convert between characters and their ASCII representations Further information on these and all the other string intrinsics are available in the EASI reference manual and on line help Files EASI provides an interface to
21. a variable that is not within the range of legal values the variable may represent the result of the assignment is undefined and should not be relied upon Arrays provide a convenient way to handle large sets of variable values of a particular type Arrays are declared like other variables using the LOCAL or GLOBAL commands but also require a size specifier in square brackets after the variable name For example an array of 3 integers called x can be declared with the command EASI gt local integer x 3 The number 3 in square brackets in the declaration statement sets the size of the array The values in an array are manipulated in expressions and assignments using indexing An index is a numeric value that is used to access a particular element of an array The first element of an array is always accessed with the index 1 and the remaining values are accessed with the indices 2 3 and so on up to the declared size of the array Indices appear in square brackets following the array name For example to assign the value 5 to the first element of the array x EASI gt x 1 EASI gt x 2 EASI gt print x 5 15 0 5 x 1 10 1 x 2 x 3 44 PCI Geomatics Chapter 4 EASI Programming Special Types The maximum size of which an array may be declared is limited only by available memory Arrays may only be declared for the basic types available in EASI byte char integer float and double and also for stru
22. also be terminated In general once a statement causing an error is executed all execution is terminated including all levels of calling functions up to the top level Control then returns to the EASI prompt and the error number and message are displayed Statement Level Error Trapping Some statements in EASI allow the programmer to trap errors through the use of the ONERROR statement suffix The general form for statements which accept the ONERROR suffix is statementl1 ONERROR statement2 106 PCI Geomatics Chapter 6 Error Handling where statementl is a statement that supports the ONERROR suffix Statement2 is any valid EASI statement to be executed only if an error occurs while executing statementl Statements which support the ONERROR suffix are LET assignment ASK RUN CALL DELETE EVAL and INPUT For example if x 0 in the Invert function presented above using the ONERROR form of the assignment LET statement provides a way for execution to continue y 1 x ONERROR y 0 y 1 x ONERROR goto ErrordHandler y 1 x ONERROR error GetLastErrorNumber In the first case shown above the variable y will be assigned the value 0 if an error occurs Note that this will occur regardless of what error actually occurred That is if the user called invert with a string instead of a numeric argument a different error would occur represented by a different error code but the error will be handled in
23. characters String parameters are used to hold character information e g file names text strings The syntax for defining a string parameter is DEF parm C default prompt where parm is the parameter name up to 8 characters cC indicates string parameter type default is a default value 0 to 12 characters prompt is a prompt message up to 32 characters Numeric parameters are used to hold up to 16 real data values The syntax for defining a numeric parameter is DEF parm N min max default prompt 26 PCI Geomatics Chapter 3 Developing Simple Scripts where parm is the parameter name up to 8 characters N indicates the numeric parameter type min is a real minimum value for data values max is a real maximum value for data values default is a real default for specified data values if this is outside the min max range it forces unspecified data values to be missing prompt is a prompt message up to 32 characters Examples DEF MESG M please enter your ID code DEF USRTEXT C NONE User text parameter DEF NTAPES N 1 16 0 Enter number of tapes Defining Input Parameters for ENHANCE EAS The method of specifying input using parameters can be applied to the ENHANCE script removing its dependence on hard coded input values ENHANCE requires three input values the name of the input file the channel within the input file containing
24. corresponding textual error message If an error occurs in EASI it normally causes execution to halt and control to return to the main EASI prompt However it is possible to trap errors and continue execution of an EASI script using the ONERROR statement suffix and the TRY ONERROR ENDONERROR construct In addition intrinsic functions exist for examining the last error code and the corresponding error message Default Error Behaviour As a simple example of the behaviour of EASI when encountering an error consider the following user defined function DEFINE FUNCTION Invert x local float y EASI User s Guide 105 Statement Level Error Trapping y 1 x return y ENDDEFINE Once the function has been loaded into EASI it can be used interactively as follows EASI gt print Invert 2 0 5 However when called with an argument of zero an error will occur EASI gt print Invert 0 E608 Divide by zero The error number 608 indicates an illegal operation was attempted in this case division by zero has occurred It is important to note that once the error happens execution immediately halts No statements after the statement on which the error actually occurred are executed in the example above the statement return y is not executed Instead the function simply terminates Similarly if the function causing the error was called from within another function or script the calling function would
25. dynamically using EAlloc the Destroy method is called when they are deallocated by a corresponding call to EFree If an object has a parent class the Destroy method of the parent class will be executed also after the objects own Destroy method Note however that if a function exits due to an EASI error the Destroy methods of local objects declared in the function will not be called A Sample Class The following definition creates a class called VLShape that allows simplified access to a shape within a vector layer It is built on top of the EASI vector intrinsics functions It serves as an example of defining and using a class It includes the use of the Initialize and Destroy methods as well as the GetDynamicField and SetDynamicField methods The complete definition of VLShape includes the class declaration which holds various information about the file and vectors being accessed and the definition of 8 methods These include an Open and Close method for initiating and terminating access to a database file First and Next methods for iterating between shapes in a vector layer Get Vertices and SetVertices methods for manipulating vertex lists and finally the dynamic field methods for accessing attribute fields belonging to a shape directly as if they were fields within the class definition The Class Definition The class definition itself holds various information about the file including the na
26. e lt less than e lt less than or equal to e gt greater than e gt greater than or equal to e lt gt not equal The numerical values being compared can be literal numeric values such as 8 or numeric variables of type byte integer float or double or an expression that evaluates to a numeric value or an indexed numeric parameter For example if an integer variable called VALUE is set to 3 then the statement if VALUE 3 gt 8 then print SUCCESS endif would result in the condition evaluating to TRUE and the print statement would be executed A logical string expression is the comparison of two strings using one of the following logical operators e equals EASI User s Guide 63 Procedure Control e lt gt not equal The two strings are compared character by character until the condition is satisfied If the strings do not match in length the shorter one is padded with blanks to yield equal lengths The comparison is not case sensitive so the strings abc and aBc are considered to be the same The two strings in the expression may be e literal strings such as abc e string variables e an indexed element of an mstring variable e a character or character array variable e a character parameter For example ifa string variable called ANSWER is set to NO then the statement if answer lt gt YES print SUCCESS will result in the condition eva
27. file if it exists and continue executing even if the deletion failed as when the file doesn t exist DELETE tmpfile pix NOERROR Error Information Functions A pair of intrinsic functions exist to allow the identification of the last error to occur GetLastErrorNumber and 108 PCI Geomatics Chapter 6 Error Handling GetLastErrorMessage These functions can be used in conjunction with the various error trapping techniques available in EASI to allow an appropriate course of action to be taken depending on the error that has occurred GetLastErrorNumber The GetLastErrorNumber intrinsic function returns the number of the last EASI error that occurred A zero is returned if no error has occurred since EASI began executing define function Invert x local integer y y 1 x ONERROR goto ErrordHandler return y ErrorHandler printf Trapped error d returning 0 n GetLastErrorNumber return 0 enddefine GetLastErrorMessage The GetLastErrorMessage intrinsic function returns the text message of the last EASI error that occurred An empty string is returned if no error has occurred since EASI began executing define function Invert x local integer y y 1 x ONERROR goto ErrordHandler return y ErrorHandler print The following error was trapped n print GetLastErrorMessage return 0 enddefine EASI User s Guide 109 Error Casting Functions Error Cast
28. in groups of 16 channels at a time local i j file hyperl pix 1 valu 128 by 16 16 for i for j dboc j endfor run clr endfor to 1 to ee Se See Also WHILE GLOBAL The GLOBAL command declares EASI variables of the requested or default type in a manner similar to LOCAL however with GLOBAL the variables will persist after the current procedure or function terminates They can also be accessed from any function or procedure GLOBAL type name Carray_size type name Carray_size name names of EASI variables to declare EASI User s Guide 157 Commands type type of variable array_size number of entries in the array Possible types include byte a single unsigned byte char a single character 1 byte double an 8 byte double precision floating point value float a 4 byte floating point value integerC int a signed 4 byte integer mstring a multi line string array no arrays pointer ptr a generic memory pointer Sung an arbitrarily long string variable no arrays mvar modeling intermediate array Vertex a structure with an x y and z field GeoInfo a structure to hold projection information Example The following example declares a globally available array of integers with 256 elements called img_lut global integer img_lut 256 See Also LOCAL GOTO The GOTO command transfers execution control to the statement at the specified
29. member functions READONLY data fields may be read any function but may not be modified by any function except methods member functions defined on the class READONLY data fields are specified by enclosing their definitions between the keywords ReadOnly and EndReadOnly For example the following definition of the Circle class will make the Radius and Area fields readonly DEFINE CLASS Circle double Centerx double Centery ReadOnly double Radius double Area EndReadonly ENDDEFINE With this new definition the CenterX and CenterY fields are still public and can be read and modified by any function local Circle c c Centerx 5 EASI User s Guide 119 Class Declarations print c Ccenterx Since the Radius and Area are ReadOnly they can be printed and used in assignments and expressions print c Area local double Spherevolume f Spherevolume 4 3 3 142 c RadiusA3 However they cannot be directly assigned to The following statement would result in an error c Radius 3 0 Private data fields are the most restricted and may not be read nor modified by outside functions and may only accessed or modified by methods defined on the class Private fields are specified by enclosing their definitions between the keywords Private and EndPrivate The following definition makes the Area field private in class Circle DEFINE CLASS Circle double Centerx double Centery Readonly double Radius EndReadonly Private
30. not procedures See Also Startup File ASK The ASK command prompts the user for a new value for the parameter ASK prompt parm ONERROR statement prompt optional prompt string to replace default prompt parm parameter file entry name ONERROR error condition handler EASI User s Guide 139 Commands For numeric parameters the value provided by the user is parsed as a comma separated series of expressions Each of the expressions is evaluated before being assigned to the corresponding entry in the numeric parameter If there is an error evaluating any of the expressions and an ONERROR statement is available it will be invoked ONERROR statements are never invoked for character parameters Example The following statement asks the user for a value to assign to the character parameter FILE and overrides the standard FILE parameter prompt ask PCIDSK Database To Create file See Also INPUT BYE The commands BYE and QUIT terminate EASI Note that the STOP command just terminates execution of a procedure returning control to the user EASI gt BYE See Also STOP CALL CALL function arguments gt mstring ONERROR statement The CALL command is used to invoke user defined or intrinsic functions Argument expressions passed to the function should be separated by commas If there are no arguments the brackets enclosing the arguments may be omitted If the CALLed 140 PCI Geom
31. print expressions may be intermixed Interactive Data Input Data can either be entered interactively at a prompt or through the use of parameters in the same way that tasks use parameters to specify input Interactive input is accomplished using the ASK command followed by a prompt enclosed in quotes and then the name of the parameter to which the data will be read ASK Enter file name file When executed this command will cause the prompt message to be printed and EASI will then wait for the user to enter the requested data which in this case will be stored in the parameter FILE 24 PCI Geomatics Chapter 3 Developing Simple Scripts Enter file name test p7x Data Input With Parameters An EASI procedure can use parameters to specify input In this case the parameters must be set by the user before the procedure is executed Pre defined system parameters may be used or new parameters may be created specially for the use of the procedure Since parameters are globally defined there is no need for formal parameter passing to procedures However to improve ease of use procedures can be made to generate status reports which are displayed when the status of a procedure is requested Status reports are useful in allowing the user of a procedure to check which parameters are used so they can be set before the procedure is run It is up to the writer of the procedure to check the values of the parameters
32. r Once the file has been opened the TextRead intrinsic can be used to read a line of data local string dataline dataline TextRead fd The TextRead intrinsic is given the handle in this case fd of the open which is to be read The first time it is called it will return the first line of the text file On each subsequent call it will return the next line of the text file When the end of the file is reached it will return the string lt EOF gt Once access to a file is no longer needed it should be closed using TextClose call Textclose fd In order to create a new file it should be opened with w access Should the file already exist its contents will be deleted Once open the new file may be written to using the TextWrite intrinsic fd TextOpen new txt w call Textwrite fd a line of text to be written to the file call Textclose fd TextWrite may be called as many times as desired to write more lines to the file Lines can be appended to the end of an existing file by opening it with a access If the file does not already exist then a new one will be created fd TextOpen file txt a 82 PCI Geomatics Chapter 5 Working with Data call Textwrite fd a line of data to be appended to the file call TextClose fd TEXT Import is a convenient intrinsic that allows an entire text file to be imported dire
33. r followed by the procedure name This is the short form of the RUN command Example r EX1 Keeping a Record of Your Work LOG The history log file allows you to keep a record of the work you have done When logging is active and you run any procedure EASI automatically generates an entry in the log file Each time EASI User s Guide 15 Keeping a Record of Your Work LOG a procedure completes a second log entry is made The log isa file on disk named EASI LOG In general the log file will consist of a list of procedures run and the times interspersed with optional entries Each log entry has the form HH MM SS operation message where HH MM SS is the current time Loperation is the type of log entry message is a short description message A sample history log might appear as 09 15 36 BEGIN EX1 RUN EX1 09 15 56 END EX1 Start Logging To start history logging enter EASI gt LOG START This will open the current log file and start adding log messages to the bottom of it If no log file exists a new one will be created To indicate that logging was started the following line is entered into the file HH MM SS LOG STARTED DD MMM YY If the log file was already open this command is ignored Stop Logging To stop history logging enter 16 PCI Geomatics Chapter 2 Using EASI EASI gt LOG STOP This will close the log file preventing any further entries To i
34. r tanneeeten cen ae E aetatetiiadaabcteatett aeels 18 Developing Simple Scripts Acoimple Procedureel 21 Interaction With ProCceCures eeecceceeeeeeteeeeeeeettneeeeeeenteeeeeeeeaees 23 Defining New Parameter Entries DEFINE eneee 25 SEEing Defaults of Parameters 0 cccccceeeeeeeeeeeeettieeeeeetnaeeeeees 28 Procedure Documentation ccccceeeeeeeeeeeeecereeeeetetieeeeeetitaeeeeeeeaa 31 Commenting Procedures REM cccccecssereeeeeesetneeeeeeetneeeeete 34 The Entire ENHANCE EAS Script eeeceeeeeeeeeeeeeeeeeeeeeeeeeeenaees 35 EASI Programming COVOIVIEW r ck chee cb adetee a Aaaa AE e A E iaraa 39 Scripts Functions and Intrinsics cccccccceseeseeeeeseeeeeeseeseeeeees 39 EASI Va ableS i iranerne eea aada a Are ea EEEE ia EEEN 41 EXpreSSIONS ne e a aaa a a aa a AEA AE relate ees 56 Procedure Controls ierden a ea erae a aeda aN 60 User Defined Functions ccccceseseseesesecececeececeeeeeseeeeesaeaeseaeeeenes 72 Working with Data VER FUG E E T AAE A O ae eadgaaie 81 Table of Contents Chapter 6 Chapter 7 Chapter 8 Appendix A Appendix B Binary FICS uaea n aAA A AE AAA dees 83 Database Files nrinn eaa i aae aa a E ea Ea 86 Projetos e a rr S EA A a A 92 Vector Data alia ee eens iene cued as aetna 95 Data Modelling sissssssees tecsageenastatepeeisiangageesddasssteeasanasiededeatnhaoteaasaneneeed 98 Error Handling OVERVIEW S ae raataa e aaa Ae ssd apn s
35. records are one line descriptions that can be associated with a file with an image channel within a file and with a data segment within a file Whenever a file is modified it is good practice to add a history record describing the change When a new record is added the previous records are pushed down Most file formats maintain the last 8 history records with each record being a maximum of 56 characters For example to write a new history record containing the message Linear Enhancement to image channel 2 of an already open file call DBwriteHistory fd IMG 2 Linear Enhancement The second argument IMG specifies that the history record is being written to an image channel and the third argument gives the channel number being written EASI User s Guide 89 Database Files A specifier of FIL as the second argument indicates that a record for the overall file should be written and in this case the third argument is ignored A specifier of LUT PCT or any other valid segment descriptor indicates that the corresponding segment type should be written and in this case the third argument gives the corresponding segment number If the processing of an image database file is aborted for some reason the data being operated on may be left in an incorrect state In this case it is useful to have a special history record written to indicate this state This is accomplished b
36. spacing in pixels for a regular grid as well as for an input and output channel local int spacing in_chan out_chan input Enter the grid spacing input Enter the input channel in_chan input Enter the output channel out_chan spacing if Cmod x spacing 0 or mod y spacing 0 then out_chan 255 else f out_chan in_chan endif Filtering Perform a 3x3 smoothing filter on channel 4 Note the use of Example backslashes to extend a statement over multiple lines Also note that PACE program FAV performs this operation more efficiently EASI User s Guide 171 Commands Numeric Expressions MODEL 7 4 x 1 y 1 4 x y 1 4 x 1 y 1 4 x 1 y 4 x y 4 x 1 y 4 0x 1 y 1 4 x y 1 4 x 1 y 1 9 ENDMODEL When processing pixels on the border of the image the neighbourhood of the current pixel will extend off the database To ensure that referenced pixels that are off the database such as 4 x 1 y 1 in the top left corner are usable the image values are replicated out from the edge of the database to supply values that are missing See Also FAV PRINT The PRINT command is used to generate output to the user s terminal P RINT expression expression expression expression a string numeric format box or PCILOGO expression The arguments to the print command are a comma separated list of numeric expressions string expre
37. string or vector valued expression If no expression is given the LET command attempts to assign a default value to the variable If the variable does not exist the LET command will attempt to create a local variable of the given name with a type depending on the type of the expression being assigned Numeric EASI User s Guide 163 Commands expressions will result in the creation of a float variable Other types such as strings and mstrings result in the creation of a variable of the same type Note that if the expression is a data reference such as a pointer structure or array a new reference to the same data is created and the actual data itself is not duplicated It is an error to attempt to default the value of an undefined variable The LET keyword is optional The ONERROR clause can be used to trap errors that occur during the evaluation of the expression or other errors during the execution of the LET statement If the ONERROR clause is activated the actual assignment will not take place although some or all of the expression may have been evaluated See Also Expression LOAD The LOAD command loads the procedure into EASI without executing it This effectively parses the procedure making all defined functions and types in the procedure available for use LOAD file file complete file specifier Note that previous forms of this command where the procedure name was not a string expression ar
38. the data to be read and the name of the output file to create Existing parameters can be used as input parameters For example the parameter DBIC can be used to specify the input channel number to ENHANCE New parameters can also be created with specific names and descriptions tailored to the script A pair of parameters called INFILE and OUTFILE can be created to specify the files used by ENHANCE as follows DEFINE INFILE C Input Database File EASI User s Guide 27 SEEing Defaults of Parameters DEFINE OUTFILE C New Output Database File SEEing Defaults of Parameters A special form of the SEE command will display the characteristics given to a parameter when it was defined The form of the command is SEE parm DEF INE where parm is the parameter name When the define option is used the SEE command will output the defined min max and defaults of the parameter along with its current value For Numeric parameters an extra line is printed Minimum gt number Maximum gt number Default gt number may be none For string parameters this extra line will be Default string 12 characters For example if EASI gt DEF NM1 N 0 10 1 Temp Numeric vector EASI gt NM1 1 2 3 then EASI gt SEE NM1 DEF NM1 Temp Numeric vector gt 1 2 3 Minimum gt 0 Maximum gt 10 Default gt none 28 PCI Geomatics Chapter 3 Developing Simple Scripts Procedure Status
39. the f value intrinsic local float x x F value 3 25 Conversely the f string function can be used to convert a numeric value to a string local string s s f string 3 25 The FindSubString intrinsic function can be used to find the location within a string ofa given substring It returns the index of the start of the substring if successful or 1 if unsuccessful The search is case insensitive EASI gt print FindSubString Pixels 256 Lines 512 lines 13 FindSubString takes an optional third argument which is the location within the string at which to start searching This can be used to continue searching for a subsequent occurrence of the string EASI gt print Coordinates X 24 Y 32 Z 18 X 23 Y 32 2 19 EASI gt print FindSubString Coordinates y 6 EASI gt print FindSubString Coordinates y 7 21 84 PCI Geomatics Chapter 5 Working with Data FindSubString can also be used to return the line within an mstring that contains a given substring For example suppose an mstring called Header contains the following data EASI gt print Header Channels 10 Pixels 256 Lines 512 8 Bit Unsigned f EASI gt print FindSubstring Header Lines 2 The FindSubString intrinsic could then be used again on the resulting line to determine the location within that line of the desired string The f extract intrinsic function will extract a substring from
40. the following criteria e All labels must be placed at the beginning of their line e All label addresses must be followed by a colon and then a statement When told to GOTO a specific label the procedure will prompt the computer to look for a specific label within the instruction rather than a line number An example that illustrates the use of a label would be local string yn print This program demonstrates using labels with GOTO statements ASKAGAIN ee Do you wish to run this program Y N yn if Cyn lt gt Y and yn lt gt N then goto ASKAGAIN endif 70 PCI Geomatics Chapter 4 EASI Programming print Thank You The label being used is ASKAGAIN Without the input of a Y or an N the program will continue to loop back to the ASKAGAIN label Once the requirements of the ZF statement are met the final PRINT statement will be executed Labels are not variables and label names are not declared at the beginning of a program with a LOCAL command Note that a backslash follows the first ASKAGAIN statement Recall that when the backslash is the last character on a line of text the next line is considered to be part of the current line There are certain circumstances where GOTO s should not be used GOTO s should not be used to exit TRY or MODEL statements these statements are described in detail in later chapters Returning RETURN The RETURN statement terminat
41. the same way by executing the ONERROR statement In the second case control will transfer to the point marked by the label ErrorHandler The function Invert should define this the label followed by appropriate code to execute if an error occurs for example define function Invert x local integer y y 1 x ONERROR goto ErrordHandler return y ErrorHandler print An error occurred while executing Invert x return 0 enddefine EASI User s Guide 107 Error Information Functions Finally in the last case the variable error will be assigned the error code which is obtained using the GetLastErrorNumber intrinsic function This error code can then be examined by subsequent code to determine a course of action define function Invert x local integer y error error 0 y 1 x ONERROR error GetLastErrorNumber if C error 0 then return y else print An error has occurred return 0 endif enddefine In the above example the code prints a message and returns zero if any error has occurred The NOERROR keyword can be used to completely suppress errors in the supported statements y 1 x NOERROR In this case if any error occurs it is ignored and execution continues with the next statement No assignment will occur and the variable y will contain the value it had before the assignment statement causing the error was executed A more common example is to delete a
42. to an argument variable will cause changes in the invoking procedure This occurs when passing arrays pointers structures and MSTRING variables For example consider another function define function IncrementArray a local integer i for i 1 to f len a a 1 a 1 1 endfor enddefine This function will add the value 1 to each element of an array The intrinsic function f len is used to determine the length of the array The function can be used as follows local integer data 5 local integer i for i 1 to f len data data i i endfor call IncrementArray data The array data is initialized to the values 1 2 3 4 5 After the function IncrementArray is called the array will hold the values 2 3 4 5 6 In this case the array is passed by reference to the function and modifications to the data within the function will affect the original data No type checking is performed on arguments when they are passed to a user defined EASI function It is possible for a function to be invoked with an argument of a type other than what was intended by the author of the function In this case 76 PCI Geomatics Chapter 4 EASI Programming execution will continue until and unless an error occurs It is possible to explicitly determine type information from a variable using the intrinsic function f partyp Refer to the reference manual or on line help for more information on this function Returning
43. variables are prefixed with two percent characters instead of one Also the index number is the segment number or graphic plane of the bitmap layer to be used n Cx_expr y_expr n x_expr y_expr Ffile_spec n Cx_expr y_expr Bitmap variables will only assume values of zero or one Any non zero value assigned to a bitmap layer will be treated as one Example Create a bitmap mask segment 2 which is true 1 everywhere channels and 2 are less than 25 Then this mask and the mask in segment 3 are used to determine a region that should be zeroed in image channels and 2 if 1 lt 25 and 2 lt 25 then 2 1 else 2 0 endif if C 2 1 2 endif 1 and 3 0 then OO ll 192 PCI Geomatics Chapter 8 EASI Language Reference Special Special variables allow access to information about the size and Variables georeferencing information of channels being operated on as well as the position of the current pixel The following special variables may be treated as elements in modelling expressions x current x pixel processing location y current y line processing location dbx size of database in x pixel direction dby size of database in y line direction meterx size of a pixel in x direction in metres metery size of a pixel in y direction in metres geox x georeferenced centre of current pixel geoy y georeferenced centre of current pixel
44. which the break is being set should already be loaded using for example the LOAD command Each breakpoint that is set is assigned a numeric identifier This identifier is used in subsequent commands to CLEAR DISABLE or ENABLE the breakpoint The BREAK ONERROR form of the command will cause debug mode to be entered automatically when an error occurs Breakpoints are removed with the CLEAR command The DEBUG CLEAR command is used to remove existing breakpoints set using the DEBUG BREAK command DEBUG CLEAR breakpoint_id DEBUG CLEAR ALL DEBUG CLEAR ONERROR Example Clear breakpoint number 1 DEBUG CLEAR 1 The DEBUG CONTINUE command is used to continue execution after it has been halted by reaching a breakpoint DEBUG CONTINUE Execution will continue until the next breakpoint is encountered or execution completes 152 PCI Geomatics Chapter 8 EASI Language Reference Disable Enable List Step The DEBUG DISABLE command is used to disable breakpoints A disabled breakpoint will not cause execution to halt when it is reached A disabled breakpoint may later be re enabled DEBUG DISABLE breakpoint_id DEBUG DISABLE ALL Example Disable breakpoint number 3 DEBUG DISABLE 3 The DEBUG ENABLE command is used to enable breakpoints An enabled breakpoint will cause execution to halt when it is reached DEBUG ENABLE breakpoint_id DEBUG ENABLE ALL Example Enable breakpoint number 3
45. A2 has a length of two but adjacent double quotes has a length of zero and is a null string In the case of a string parameter the null string may be interpreted as a missing value Some application tasks may require non null string s before executing Subscripted Parameters Each of the 16 elements in a numeric parameter and the 64 characters in a string parameter can be individually accessed through the use of subscripting This has the form parm Cnumexp where parm is a defined parameter 10 PCI Geomatics Chapter 2 Using EASI numexp is a numeric expression used as a subscript Subscripts start with a value of 1 For example if TEXT has the value ABCD123 then TEXT 3 addresses the third position which contains the value C If VECTOR has the values 1 3 5 2 then VECTOR 2 addresses the second position in VECTOR which contains the value 3 This subscripting capability is useful for loop control list checking and limited forms of text manipulation These programming techniques will be introduced over the next few chapters Setting and Changing Parameters Variables LET During the course of work the normal progression is to decide which procedure to run examine the parameters that control it perhaps modify some of them and then actually run the procedure The LET command allows you to change the current value of a parameter Its two most common forms are LET parm number numb
46. ASI and can be used to test if a pointer is currently pointing to any data if pData NULL print The pointer is set to NULL A block of memory can be allocated using the EAlloc intrinsic function EAlloc takes two arguments the first is the type of the memory and the second is the number of units of memory of that type to allocate To allocate a block of 10 integers use the statement pData EAlloc int 10 The actual data being pointed to can then be manipulated using array style indexing pData 1 pData 2 10 pData 1 5 The length of the block of data being pointed to can be obtained using the FSLEN intrinsic function EASI gt print f len pData 50 PCI Geomatics Chapter 4 EASI Programming 10 Pointers can be assigned to other pointers local int ptr pData2 pData2 pData In the above example pData2 will be pointing to the same data as pData EASI gt pData2 3 100 EASI gt print pData 3 100 A block of data can be reallocated to a larger size using the ERealloc intrinsic function ERealloc takes the same arguments as EAlloc along with a third argument which is a pointer to the block of memory to be allocated to a larger size pData ERealloc int 20 pData When a block of data is reallocated to a larger size it may be necessary to move it within memory to a new location EASI manages this automatically The previous contents of the block of data w
47. BNextSeg fd LUT segnum endwhi le printf The file contains d look up tables n NumLUTs Closing a Database File Once file access is completed the file is closed using the DBClose intrinsic call DBClose fd Projections Projections are coordinate systems used for representing points on the Earth EASI includes intrinsic functions for accessing projection information from database files and for translating points between projections Projection information is stored in EASI in a pre defined structure named GeoInfo define structure GeoInfo charUnits 24 Map Units string at most 16 lon doubleuULX Upper left X coord georef units doubleULY Upper left Y coord georef units doubleLRX Lower right X coord georef units doubleLRY Lower right Y coord georef units doubleDEarth1l doubleDEarth2 doubleRefLong Reference Longitude 92 PCI Geomatics Chapter 5 Working with Data doubleRefLat Reference Latitude doubleStdParallell doubleStdParallel2 doubleFalseEasting doubleFalseNorthing doublescale doubleHeight doubleLong1 doubleLatl doubleLong2 doubleLat2 doubleAzimuth integerLandsatNum integerLandsatPath enddefine Database files often have projection information stored with them The projection of a database file can be read into a Geolnfo structure using the DBReadGeoInfo intrinsic and written to the file using the DBWriteGeoInfo intrinsic For example to read proje
48. EASI User Guide Version 9 0 May 2003 50 West Wilmot Street ww Pi I Richmond Hill Ontario Canada L4B 1M5 gt Phone 905 764 0614 Geomatics Fax 905 764 9604 Committed to GEO intelligence Solutions Email support pci geomatics com 2003 PCI Geomatics Enterprises Inc All rights reserved COPYRIGHT NOTICE Software copyrighted c by PCI Geomatics 50 West Wilmot St Richmond Hill Ontario CANADA L4B 1M5 Telephone number 905 764 0614 RESTRICTED RIGHTS Canadian Government Use duplication or disclosure is subject to restrictions as set forth in DSS 9400 18 General Conditions Short Form Licensed Software U S Government Use duplication or disclosure is subject to restrictions as set forth in FAR clause 52 227 19 Commercial Computer Software Restricted Rights and in subparagraph c 1 ii of the Rights in Technical Data and Computer Software Clause at DFARS 52 227 7013 ACE ACE amp Design logo ACE Advanced Cartographic Environment AGROMA EASI PACE EOScape FLY GCPWorks GeoAnalyst GeoGateway ImageWorks OrthoEngine PCI OrthoEngine PCI PCI amp Logo Committed to GeoIntelligence Solutions PCI Author PCI Visual Modeler RADARSOFT RasterWorks and SPANS are registered trademarks of PCI Geomatics Enterprises Inc PCI Geomatics and Geomatica are registered trademarks of PCI Geomatics Enterprises Inc InstallShield is a registered trademark of InstallShield Software
49. I gt status enhance The user of the script will then be able to set the parameters to appropriate values as with any other EASI task Procedure Documentation Procedure Help The DOC statement is used to enter on line help documentation for procedures This statement has the form DOC text where text is any character text to the end of the line When requesting help for a procedure EASI will scan the procedure and print to your screen the text associated with every DOC statement it finds until it encounters a subtopic a DOC_END statement or the end of the procedure It is standard practice to put DOC statements at the beginning of a procedure EASI User s Guide 31 Procedure Documentation A special form of the DOC statement is used to identify subtopics Subtopic identification lines have the form DOC topic where is a subtopic level from 1 to 9 topic is a 1 to 15 character subtopic identifier Note There must be only one space between the DOC statement and the subtopic level number Also note that during procedure execution DOC lines are ignored like REM statements DOC statements associated with subtopics are only printed when the user requests them The EASI help system will automatically scan the procedure and list the subtopics of any topic the user chooses Example DOC This is an example of on line documentation DOC 1 FIRST DOC This line is associated with subtopic FIRST
50. Programming If the variable a is set to the value 3 then the print statement is executed Ifa is not set to 3 then the print statement is ignored For a complete discussion on conditions see the section on logical expressions Any valid EASI statement can be put in place of the print statement Note that when the equals operator is used in an if statement it is used as a test of equality and no assignment is performed This is unlike the usual use of the equals operator outside of an if statement where it will cause variable assignment to take place A more complex form of the if statement allows the execution of a block of statements if the test is satisfied instead of just a single statement if condition then statement list endif where statement list is a list of command statements to execute if the condition is true For example if channel gt 10 then print Error channel is too large print Channel will be reset to default value of 1 channel 1 endif There may be an arbitrarily long list of statements between the if and endif statements to be executed if the result of the condition is TRUE If the condition evaluates to false then the next statement to be executed is the first statement after the endif Note that a common source of syntax errors is accidently omitting the then keyword at the end of the if statement The use of an else clause with the if statement allows a se
51. RN statement is used without an expression to return it simply causes the function to terminate just as if it reached the end of the function definition Variable Argument Lists It is possible in EASI to define a function that takes a variable number of arguments This is accomplished by using the VARARGS keyword in the function definition s argument list and the intrinsic function of the same name within the body of the function to access the additional arguments The VARARGS keyword always appears at the end of the functions argument list after any number fixed arguments possibly none For example a function which takes a minimum of two arguments followed by any number of additional arguments can be defined using a definition that starts with define function v a b varargs 78 PCI Geomatics Chapter 4 EASI Programming Once defined the function can be called with two or more arguments Within the body ofa function that uses VARARGS the number of additional arguments can be determined using the FSLEN intrinsic and each of the arguments can be extracted by calling the intrinsic function VarArgs with the number of the argument to extract The following is a variable argument version of the Max function presented earlier define function vmax argl arg2 varargs local double Maximumvalue local integer i MaximumValue argl if arg2 gt Maximumvalue then Maximumvalue arg2 endif for i 1 t
52. Reference DOC The DOC command marks a line of text as documentation rather than commands This documentation is used for on line help DOC text text any line of text EVAL The EVAL command is used to evaluate an EASI subprogram provided as a string argument This accomplishes approximately the same thing as writing the string expression to a file and then running it using the RUN command EVAL prog_line ONERROR statement prog_line string expression to be evaluated as a subprogram The subprogram must be a single string expression not a multi line expression but it may contain many logical lines separated by backslash characters An ONERROR clause may be added to perform a statement if an error occurs The EVAL command exists so that procedures can easily evaluate arbitrary expressions created at run time The evaluated sub expression has its own variable scope similar to a subprogram invoked with CALL or RUN No value is returned so results are normally exported only via side effects Example A user enters a parameter name and the value is extracted and assigned to NUM EASI User s Guide 155 Commands local string var_name int error input Parameter Name var_name error 0 EVAL NUM1 var_name ONERROR error 1 if error 1 then print var_name is not a legal numeric parameter else print var_name value is num1 endif FOR The EASI FOR command provides a simple l
53. Values The return command is used to terminate the execution of a function and to optionally return a value The syntax of the return command is return optional_expression where optional_expression is a value or expression to evaluate and return The following function returns the maximum of two values define function Max a b local integer Maximumvalue if a gt b then MaximumValue a else Maximumvalue b endif return Maximumvalue enddefine This function requires two arguments and will return a single value using the RETURN command Functions that return a value are not executed using the CALL statement since the CALL statement will not allow use of the value returned by the function However functions that return a value can be used within any expression For example they can be used in print statements print Max 3 6 Or they can be used in assignments EASI User s Guide 77 User Defined Functions m Max 3 6 Or they can be used in calls to other functions m Max Max 3 6 1 In the last case the function Max is called with two arguments one of which is the expression Max 3 6 which evaluates to 6 When the statement executes the variable m will be assigned the value 6 A function can have more than one return statement The Max function could also be coded as define function Max a b if a gt b return a return b enddefine When the RETU
54. a pixel in x direction in metres metery size of a pixel in y direction in metres geox x georeferenced centre of current pixel geoy y georeferenced centre of current pixel sizex x size of a pixel in georeferenced units sizey y size of a pixel in georeferenced units In addition to the modelling expressions described above the body of a MODEL statement may include other EASI statements such as IF statements to perform more complex operations Modelling Examples Perform a 3x3 smoothing filter on channel 4 Note the use of backslashes to extend a statement over multiple lines EASI User s Guide 101 Data Modelling Grid Example MODEL 67 4 x 1 y 1 4 x y 1 4 x 1 y 1 4 x 1 ay 4 x y 4 x 1 y 4 x 1 Gy 4 x y 1 4 x 1 y 1 j 9 ENDMODEL When processing pixels on the border of the image the neighbourhood of the current pixel will extend off the database To ensure that referenced pixels that are off the database such as 4 x 1 y 1 in the top left corner are usable the image values are replicated out from the edge of the database to supply values that are missing A file is georeferenced in UTM coordinates As part of the final processing steps the user wishes a grid to be superimposed on the imagery along 1000 metre intervals in both the x and y directions The input imagery is an RGB enhanced image on channels 1 2 3 The output will be to channels 7
55. ac r e aE E a daa a a 105 Statement Level Error Trapping cccceceeeeeeeeeeeeeteeeeeeeeeeeeees 106 Error Information FUnctions cccceeeeeeeeeeeceeceeeeeeeeeeeeeeeeeeneeaes 108 Error Casting FUNCIONS eere or E E AEE 110 Trapping Errors in Blocks of Code ccceeeeeeeeeeeeeteecteeeeeeeeees 111 Object Oriented Programming With EASI OVOEIVIOW so belertacereeinaeedevees cededels teddies o aaa dees degen aaiae ea eaaa 117 Class Declaration Snin nete e an 118 A Sample Classi uaiiie eener ea ae et 126 EASI Language Reference Command Saadi rapae ae ea a adaa a aa eee 137 EXPreSSi nS a a aa aaae aa daea aaa ea aa aee aLa NEA 185 PUI CUOINS EA EE E E A EAE EEA E saika 194 Note Ssa heiste a r a a a ath eed a Naa 198 Error Message List sseeeeeceeeeeeeeseeeeeeeeeeenenneeeeneeeeees 203 System Parameter Definitions EASI System Parameters ccccccecceeeceeeceeeeeeeenieeeeeeenneeeeeeenaees 205 Nder iesseSedctvssncectecetacstbeccdetseeessacdieteceslidecbedstessecesnacaseseabtes 207 PCI Geomatics Introduction Purpose of EASI EASI the Engineering Analysis and Scientific Interface is both a command environment for interactive executing tasks and a scripting language for the construction of applications EASI is independent of its host environment and eliminates the differences between host operating systems presenting the user with a simple powerful environment As acommand environment
56. adians degrees ABS N absolute value INT N integer part of value FRAC N fractional part of value MOD N modulTus note 3 FLOOR N Targest integer smaller than value CEILING N Targest integer larger than value ROUND N nearest integer to value MIN N smalTest value in list note 4 MAX N Targest value in Tist note 4 Note 1 magnitude of the argument must not be greater than 1 194 PCI Geomatics Chapter 8 EASI Language Reference e Note 2 argument must be greater than 0 e Note 3 compute modulus of first argument relative to second argument e Note 4 takes any number of arguments from 1 to 128 Examples print Tangent of 45 degrees TANCRAD 45 Previous versions of EASI required all mathematical functions to be prepended with F i e FSTAN This notation is still accepted but not encouraged All of the functions listed above will also work in modeling expressions except for MIN and MAX Core Intrinsic Functions and Classes EASI s core intrinsic functions and classes are described in an Appendix to the Focus online Help This appendix covers Table 5 AddGrouplcon AddShared ChangeProtection CloseAllEASIFiles CopyFile CreateGroup DBChanType DBChannels DBClose DBCreate DBDelete DBExecuteScript DBGetBinaryLength DBGetChanInfo DBHashImage DBHashVector DBImageHistogram DBLines DBMouseEventRead DBNextSeg DBOp
57. andom ReCastEASIError Reproject RunTask SetCWD SetEnv SetGeolnfoParm SetRegistry SetRegistryPCl SetupNCPolling Sleep TEXT Export EASI User s Guide 197 Notes Table 5 TEXT Import TEXTClose TEXTOpen TEXTRead TEXTWrite TapeClose TapeControl TapeOpen TapeRead TapeStatus TapeWrite TmpNam Tokenize VECAd dField VECClearLayer VECCreateLayer VECCreateShape VECGetField VECGetFieldCount VECGetFieldFormat VECGetFieldName VEC GetFieldType VECGetSelection VECGetVertices VECNextShape VECQueryAttribute VECQueryNearest VECQueryRadius VECQueryRect VECReadGeolInfo VECSetField VECSetSelection VECSetVertices ae tah at VECWriteGeolnfo VarArgs This online Help reference is updated periodically as new intrinsic functions and classes are added to EASI Notes The following topics contain additional information that may be useful 198 PCI Geomatics Chapter 8 EASI Language Reference Statement Syntax A statement in EASI is the basic unit of operation A statement consists of an optional line number or line label followed by a command Note that line numbers and line labels may not appear on a line all by themselves or on lines that are part of a multi line statement such as the ENDIF of an IF construct or the ENDFOR of a FOR loop Normally each st
58. annels 1 and 2 saving the result to channel 7 If channel 7 is 32 bit real the following model is used MODEL ON irvine pix OVER dbiw 7 1 2 1 2 ENDMODEL If channel 7 is 8 bit some scaling and adjustment is necessary MODEL ON irvine pix OVER dbiw 7 1 2 14 2 128 127 5 ENDMODEL Create an image which smoothly blends channel into channel 2 as we move across the image The output is placed in channel 7 In this case we want to operate on the whole default database The default database in this case is implied by the FILE parameter The MODEL command does not have to be explicitly listed as it is implied by the channel variable in the equation FILE irvine pix 7 x 1 dbx 2 dbx x dbx 1 Create a grey level ramp of 0 to 255 across an image plane model on filo 7 C x 1 255 dbx endmodel 170 PCI Geomatics Chapter 8 EASI Language Reference See Also TIG Grid A file is georeferenced in UTM coordinates As part of the final Example processing steps the user wishes a grid to be superimposed on the imagery along 1000 metre intervals in both the x and y directions The input imagery is an RGB enhanced image on channels 1 2 3 The output will be to channels 7 8 and 9 if Cmod geox 1000 lt sizex or a se tee then 7 55 8 255 9 255 else 7 1 8 2 9 3 endif The following model prompts the user for the
59. apped and examined but no appropriate way to handle it could be determined so it is re cast as if it was never trapped Re casting the error allows it to then be trapped by a higher level error handler in another block of code or for the error to cause processing to halt and control to return to the main EASI prompt See the error handling example at the end of this chapter for an example of this function s usage Trapping Errors in Blocks of Code The TRY statement provides a convenient syntax for trapping and handling errors that occur within blocks of code It is normally used in conjunction with the GetLastErrorNumber EASIError and ReCastEASIJError intrinsics providing a powerful and flexible technique for generating and trapping errors The general form of the TRY command is TRY statement_list_1 ONERROR statement_list_2 ENDONERROR where statement_list_1l One or more statements to be executed normally statement_list_2 One or more statements to be executed only if an error occurs while executing statement_list_1 When execution reaches a TRY statement the statements in the block immediately after TRY will be executed If no error occurs during the execution of this block of code then control EASI User s Guide 111 Trapping Errors in Blocks of Code will continue with the next statement after the entire TRY ONERROR ENDONERROR clause If however an error does occur anywhere within the block the
60. array_sizem EndPrivate ENDDEFINE Note that an array size specifier should not be used if the field is of type String or MString The ReadOnly EndReadOnly and Private EndPrivate keywords can be used to declare special access restrictions on some data fields The ReadOnly field can only be updated by methods of the class Private fields can only be read and updated by methods of the class The INHERITS keyword can be used to specify a base class for the newly defined class If this is done then all fields and methods previously defined on the base class will be included in the new class This implements single inheritance Multiple inheritance is not supported Example Define a class called Circle with two initialization methods DEFINE CLASS Circle ReadOnly double Centerx double CenterY double Radius double Area EndReadonly ENDDEFINE DEFINE METHOD SetCenter x y ON Circle this Centerx x this Ccentery y ENDDEFINE DEFINE METHOD SetRadius new_radius ON Circle 146 PCI Geomatics Chapter 8 EASI Language Reference Method this Radius new_radius this Area 3 1415927 this Radius this Radius ENDDEFINE The DEFINE command can be used to define new methods on user defined or predefined classes A method is similar to a function except that it is associated with objects of a particular type Class DEF INE METHOD method_name argl arg2 eet ON class_name easi_command_list ENDDEFINE
61. assed to the operating system In this case all arguments on the EASI command line to ls will be put inside the string passed to the operating system alias Ils system Is Is pix Example 3 The following more complex example sets up an alias called clear which takes two arguments The first is the name of a PCIDSK file and the second is an image plane to clear to zero Note that the quotes and the backslashes in the alias string have to be escaped with the backslash 138 PCI Geomatics Chapter 8 EASI Language Reference alias clear file 1 dboc 2 valu 0 run clr clear eltoro pix 1 clear irvine pix 1 2 3 The arguments are determined from the command line string by breaking on white space Hence in the above example the channel list 1 2 3 is taken as one argument There are limits to what can be accomplished with the aliases alone however aliases can be used to invoke a user defined function passing all the arguments as a single string This user defined function can then parse the arguments however it pleases Example 4 The following example demonstrates this without showing what the user defined function editfunc does to parse the passed arguments alias edit call editfunc edit file irvine pix segment 11 Currently there is no command to remove aliases once instituted and it is important to remember that aliases are only applied to interactive input
62. atement appears on it s own line Blank lines are also legal Examples run ivi 100 run ivi POR user_answered_yes run ivi Multiple lines can may be placed on the same line by separating the statements with a statement separator The backslash and semi colon characters can be used interchangeable for this purpose A line of input may be almost any length Examples file pci demo irvine pix run ivi file pci demo irvine pix run ivi It is also possible to split very long statements over multiple lines by placing a backslash character but not a semi colon at the end of each incomplete line Example this_string one_long_string a_second_long_string another_long_string a_really_long_long_string a_short_string EASI User s Guide 199 Notes Startup File To facilitate the tailoring of the EASI execution environment it is possible to read a set of EASI commands from a startup file each time EASI starts On Unix the startup file is named easirc and may appear in the local directory or the users home directory as determined from the HOME environment variable On VAX VMS and OpenVMS systems the file is named EASIRC EAS and must be in the local directory On Windows Windows NT and OS 2 systems the file is named EASIRC EAS and may be in the local directory or at the top directory of the current disk The startup file is run as if it where a normal procedure and may hol
63. atics Chapter 8 EASI Language Reference function has a return value it will be discarded when the function is invoked using the CALL statement In order to capture all terminal output of a subprocedure the gt redirection clause may be used All text output of the subprocedure will be captured and placed in the provided multi line string variable type MString The statement supports an optional ONERROR statement which will be invoked if an error occurs during processing of the called function Alternatively the NOERROR postfix may be used instead of using ONERROR with a statement L Note Functions with return values can also be invoked directly from within an expression Example CALL DBOpen abc txt r CALL DBClose abc txt ONERROR PRINT DBClose failed CASE ype casel linel case2 line2 expr iS a numeric or string expression casen iS a numeric expression if expr is numeric or is a string expression of expr is a string linen is a line number or line label EASI User s Guide 141 Commands Parameter The CASE statement allows multiway branching to any line within the same procedure or function depending on the matching of one of a number of conditions The test expression expr is evaluated and then sequentially compared to the values casel case2 etc When a match is found control then branches to the line corresponding with the line number or line label follo
64. attributes belonging to the first shape shape VECNextShape fd layer 1 for attribute 1 to NumberofAttributeFields print VECGetFieldName fd layer attribute veccetField fd layer shape attribute endfor The vertices for a given shape can be are obtained using the VECGetVertices intrinsic function This function returns a pointer to a list of Vertex structures which must be freed using EFree when finished with The following code extracts and prints all of the vertices belonging to the first shape local Vertex ptr Vertices vertices VECGetVertices fd layer shape for index 1 to f len vertices printf Point d X f Y F Z f n index Vertices index x Vertices index Y Vertices index Z endfor call EFree Vertices EASI User s Guide 97 Data Modelling Intrinsic functions also exist to write a list of vertices to a shape VECSetVertices to set attribute fields VECSetField to create vector layers VECCreateLayer to create new shapes VECCreateShape and to add new attribute fields to all the vectors in a layer VECAddField Further information on all of the vector intrinsics can be found in the on line help Data Modelling EASI provides a powerful and convenient way to manipulate image data in database files through the use of its modelling facility The MODEL command is used to introduce a block of commands which are to be applied over an area
65. bject Oriented Programming With EASI Overview EASI supports object oriented programming The subject of object oriented programming in general is addressed in a large body of literature much of which can be applied to the implementation in EASI Among the benefits for this style of programming are the promotion of code reuse increased reliability through data hiding and a more balanced emphasis on data as well as function in software design Primary to EASI s support of object oriented programming is the definition of classes Classes tie together both data and functions A class can be defined to contain data of various types in a manner similar to structures Unlike structures however access to data within a class can be restricted An instance of a particular class is called an object and each object has its own copy of all the data fields defined in the class Functions that are associated with a class are called methods and act on instances or objects of the class A class may be defined to inherit both data fields and EASI User s Guide 117 Class Declarations methods from another parent class and can enhance or specialize the capabilities of the parent class by adding additional data fields and methods and by superseding methods of the parent class with new versions Class Declarations A class is created in a manner similar to a structure using the DEFINE command A simple class declaration has
66. by each program Searching For Parameter Names SEE The SEE command is used to search for parameters This is useful when you cannot quite remember how a parameter was spelled or if you wish to see a group of parameters which have similarly spelled names This command has the form SEE parm define where parm is one to eight characters of the name of a group of parameters to search define is an option that will show the defined minimum maximum and default values of that parameter Running Procedures RUN Once you have set up the parameters for a procedure using LET and checked them using SEE or STATUS you can RUN the procedure This command has the form RUN name 14 PCI Geomatics Chapter 2 Using EASI where name is the name of the procedure you wish to run Type the following EASI gt FUNCTION ROOT EASI gt VECTOR 1 2 EASI gt RUN EX1 The following should appear on your screen The square root of 1 000 is 1 0000 The square root of 2 000 is 1 4142 Type EASI gt FUNCTION SQUARE EASI gt RUN EX1 You should see the squares of the two given VECTOR values The square of 1 000 is 1 0000 The square of 2 000 is 4 0000 Try experimenting with EX1 Remember that once EASI completes a procedure it will tell you it is ready for another command by returning the EASI gt prompt To expedite your work instead of typing RUN each time you wish to execute a procedure just type R or
67. cally used in conjunction with the FSFERRNUM EASIError and ReCastEASIError intrinsics TRY statement_list_l ONERROR statement_list_2 ENDONERROR statement_list_1 One or more statements statement_list_2 One or more statements to be executed only if an error occurs while executing statement_list_l When execution reaches a TRY ONERROR ENDONERROR clause the statements after TRY will be executed statement_list_1 If no error occurs during the execution of this block of code then control continues with the next statement after the entire TRY ONERROR ENDONERROR clause If however an error does occur then control will immediately be transferred to the statements after ONERROR statement_list_2 After the error handling has been executed control continues with the next statement after the TRY ONERROR ENDONERROR clause Example Define a simple procedure to compute frequency from period It returns a large value if period is zero and raises an error if some other error is encountered such as a non numeric value for period DEFINE FUNCTION freq period local double frequency local int error TRY EASI User s Guide 183 Commands frequency 1 period ONERROR extract the error error F ERRNUM if the error was divide by zero then set frequency to a large value IF error 608 THEN frequency 1 0e 10 otherwise something unexpected happened re cast the error ELSE ReCastEASIErr
68. ck up the help levels towards the larger parent topic Pressing lt cr gt one or more times will eventually get you out of the on line help facility and back to the EASI gt prompt Parameters This section details the information needed to understand how parameter values interact with application programs and EASI commands Numeric Parameters Numeric parameters are vectors of 16 real elements During the definition of the parameter a lower bound and upper bound are specified which define the range of values the elements may EASI User s Guide 9 Parameters take An attempt to assign a value outside of this range to an element would result in an error Elements which have never been assigned a value are said to be missing or undefined Elements may be missing elements as a result of an assignment or LET command For example VECTOR 1 2 sets the first two elements of VECTOR to 1 and 2 the other 14 values to missing During parameter definition a default value is also specified This value may or may not be in the range allowed by the upper and lower bounds During the execution of application tasks this default is used for missing elements String Parameters A sequence of characters enclosed in double quotes aBc is called a string String parameters vary in length from 0 zero to 64 characters A string with no characters in it i e has a length of zero is called a null string For example
69. cond block of code to be executed if the condition tested in the if statement fails EASI User s Guide 61 Procedure Control if Ccondition then statement listl else statement list2 endif For example if a gt b then max a else MAX b endif Finally the elseif clause can be used to test additional conditions in an if statement if Ccondition then statement listl elseif condition then statement list2 else statement list3 endif For example if C NumberoOfPixels lt 1 then print window is too small elseif NumberofPixels gt 100000 then print window is too large else print window size is acceptable endif The else clause may be omitted and there may also be any number of elseif clauses instead of just one If statements may be nested within other if statements in this case it is very useful to use indentation to make the program logic easier to understand 62 PCI Geomatics Chapter 4 EASI Programming Logical Numeric Expressions Logical String Expressions Logical Expressions Logical expressions are special statements that evaluate to either TRUE or FALSE Note that there is currently no way to directly represent a logical value in EASI There are two basic types of logical expressions Numeric and String Logical numeric expressions are simply the comparison of two numeric values using one of the following relational operators e equals
70. ction TEST file TEST EAS line 15 Halted at function TEST file TEST EAS line 15 if C dataline i lt min_val min_val dataline i EASI DEBUG 1 gt EASI User s Guide 149 Commands Limitations The special DEBUG prompt is printed indicating that execution is halted during the execution of a script The current values of variables can be examined EASI DEBUG 1 gt print i 0 EASI DEBUG 1 gt print min_val 257 EASI DEBUG 1 gt print dataline i array of 512 INTEGER s at 0x8347b48 The value of dataline i dataline 0 is unexpected In fact arrays in EASI are indexed starting at the value 1 instead of 0 as in C This is the source of the bug Execution of the program is halted EASI DEBUG 1 gt debug quit EASI gt The code can now be modified changing line 14 to for i 1 to num_pixels After rerunning the program it now results in the following output EASI gt run test The minimum value is 50 The maximum value is 81 This is the correct result that was desired The following limitations exist in the current implementation of EASI DEBUG support The line numbers of ENDFOR statements are wrong and will appear to be garbage values when an ENDFOR statement is reached An IF statement with an in line statement to execute when the test is true is really two statements on one line If the test is 150 PCI Geomatics Chapter 8 EASI Language Reference Abbreviatio ns Break
71. ction information into a GeoInfo structure called gi local GeoInfo gi local Integer fd fd DBOpen irvine pix r call DBReadGeoInfoC fd gi printf Projection String s n gi Units Similarly a projection information can be written to a database file using the DBWriteGeolInfo intrinsic The following example creates a new database file using the DBCreate intrinsic and writes to this file the projection information previously read into gi The database created in this case will be a TIFF file local integer fdnew fdnew DBCreate new tif TIF DBPixels fd irs DBLines fd 1 DBChanTypeC fd call DBWriteGeoInfo fdnew gi call DBCloseC fdnew call DBCloseC fd EASI User s Guide 93 Projections The Reproject intrinsic function can be used to translate coordinates between projections This function takes a list of coordinate pairs stored in an array and a pair of GeoInfo structures defining the input and output projections as input On return the array will contain the corresponding coordinates in the output projection For example to translate the coordinates the coordinates of the upper left and lower right corners of the input projection to Long Lat local GeoInfo go go units LONG local double plist 4 plist 1 gi ULXx plist 2 gi ULY plist 3 gi LRxX plistl4 gi LRY printf ulx g uly g n plist 1 plist 2 printf 11x g lly g
72. ctly into an MSTRING It requires only the file name as an argument and there is no need to open and close the file to use TEXT Import local mstring textdata textdata TEXT Import filename txt Similarly TEXT Export allows an mstring to be written directly to a text file call TEXT Export newfile txt textdata Binary Files Access to binary files is accomplished in a very similar fashion using the DKOpen DKClose DKRead and DK Write commands Unlike the text access commands which operate on a line by line basis the binary access commands allow data to be read from and written to specific places within the file Further information on these commands is available in the EASI reference manual and in the on line help Direct access to binary files is useful to allow access to un supported file types If sufficient file format information is available it is often possible to write file format translators in EASI Manipulating Strings A set of EASI intrinsic functions perform useful operations on strings The length of a string is given by the f len intrinsic function EASI User s Guide 83 Binary Files EASI gt print f lenC file 4 The case of a string can be changed using the f upcase and f lowcase intrinsic functions as follows EASI gt print f upcase abc ABC EASI gt print f lowcase ABC abc A numeric value stored within a string can be extracted using
73. ctures which will be described later It is not currently possible to declare multi dimensional arrays in EASI Arrays of characters may be handled in a simplified way in addition to being manipulated using the indexing technique described above It is possible to assign a list of characters enclosed in double quotes commonly referred to as a string directly to the array For example EASI gt local char filename 8 EASI gt filename irvine EASI gt print filename irvine It is still possible to access individual elements of the character array using indexing EASI gt print filename 3 v If an assigned string is too large to fit within the size allocated for the array the assigned string is truncated EASI gt filename irvine pix EASI gt print filename irvine p In addition to the 5 basic types EASI provides three special types of variables These are the STRING MSTRING and MVAR Table 2 Special Variable Types and Descriptions String arbitrarily long string of characters Mstring multi line string EASI User s Guide 45 EASI Variables Table 2 Special Variable Types and Descriptions Mvar modelling intermediate array A string is very similar to an array of characters except that its size is not fixed as it is for an array of characters This makes a string very convenient to use local string name name John name John Smith name EG GG EASI automat
74. d any commands that could be placed in a procedure Typically the startup file is used to establish aliases but it can also be used for a number of other purposes The startup file is invoked before the initial prompt appears See Also ALIAS Reserved Words The following keywords are reserved by EASI and can not be used as identifiers such as variables names functions or types An attempt to use these keywords as identifiers will result in a syntax error Table 6 ALIAS BYE CASE CLEAR DEFINE DEL DELETE DOC DOC_END ELSE ELSEIF ENDDEFINE 200 PCI Geomatics Chapter 8 EASI Language Reference Table 6 ENDFOR ENDIF ENDMODEL ENDONERROR ENDPRIVATE ENDREADONLY ENDWHILE EVAL EXIT GOTO H HELP IF KEY LET LIST LOAD LOG METHOD NOERROR P PRINT PRINTF PRIVATE PTR QUIT READONLY REM RETURN RUN START STATUS STATUS_END STATUS_S STATUS_SHOW STATUS_TITLE STOP SYS SYSTEM THEN UNDEFINE WHILE EASI User s Guide 201 Notes 202 PCI Geomatics Error Message List This appendix lists in alphabetical order all the error messages generated by EASI These error codes define classes of errors Each error will have additional textual information provided in the error message EASI will also print error messages of the form E600 Type Mismatch This error indicates that the incorrect data type was used when passing an argument to a function or assignin
75. d the ENDIF If none of the logical expressions is true and an ELSE clause exists the associated statement list will be executed Example ifC f inputQ x then goto Exit elseif f inputQ then goto PromptAgain else print An error has occurred f input endif See Also Logical Expression WHILE FOR IMPORT The IMPORT command is redundant In the past it was used to allow access to variables declared with the GLOBAL statement but now all variables declared with the GLOBAL statement are available in all functions and procedures See Also GLOBAL EASI User s Guide 161 Commands INPUT The INPUT command prompts the user with text and waits for user input to the EASI variables If ONERROR is specified it overrides normal error reprompting INPUT text locvar locvar ONERROR statement text text string used for prompt locvar EASI string or EASI numeric variables ONERROR error condition handler For numeric variables the input provided by the user is parsed as a comma separated series of expressions Each of the expressions is evaluated before being assigned to the corresponding numeric variable If there is an error evaluating any of the expressions and an ONERROR statement is available it will be invoked ONERROR statements are never invoked for character input Example input Enter the X Y location in UTM Metres UTMX UTMY See Also ASK KEY The KEY command is used
76. database that can hold various types of auxiliary information such as look up tables vector data and ground control points For example look up tables can be accessed using the DBReadLUT and DBWriteLUT intrinsics The following example will read the look up table in segment 5 of the already open file referred to by the handle fd local byte LookUpTable 256 call DBReadLUTC fd 5 LookUpTable Similar functions exist to manipulate Pseudo color tables DBReadPCT and DBWritePCT Segments of a particular type may be located within a database file using the DBNextSeg intrinsic For example to locate the first segment of type LUT local int segnum segnum DBNextSeg fd LUT 1 The second argument to DBNextSeg is the segment type to be searched for and must be one of PCT LUT BIT VEC GCP TEX SIG BIN ARR or ORB The third argument is always 1 to find the first segment of the given type To find the subsequent segment of the given type the result from the previous call to DBNextSeg should be given as the third argument DBNextSeg will return 1 if no further segments of the given type could be found EASI User s Guide 91 Projections The following example counts the number of LUT segments in the database file local integer NumLUTs segnum DBNextSeg fd LUT 1 while segnum 1 NumLUTS NumLUTs 1 segnum D
77. double Area EndPrivate ENDDEFINE An attempt to print or use a private field in an expression anywhere except within a method belonging to the fields class will result in an error A class definition may contain any number of ReadOnly EndReadOnly and Private EndPrivate constructs in any order and each such construct may contain any number of individual field definitions 120 PCI Geomatics Chapter 7 Object Oriented Programming With EASI Member Functions Member functions called methods are not defined within the class definition itself Rather they are defined separately in a manner similar to regular function definitions DEFINE METHOD method_name Cargl arg2 ON class_name easi_command list ENDDEFINE For example suppose the class Circle has been defined as follows DEFINE CLASS Circle ReadOnly double Centerx double Centery double Radius double Area EndReadonly ENDDEFINE Then a method to set the centre of a circle could be defined DEFINE METHOD S TSE y ON Circle this Centerx this CenterY ENDDEFINE y The special identifier this is available automatically in all methods and is used to access the data fields and other methods ofthe object being acted upon Methods are able to access and modify data fields belonging to the objects on which they are invoked regardless of the access restrictions on those fields A method is invoked through an object instance using the dot no
78. e lost The advantage of using local variables is that by declaring variables local the user is guaranteed that no other procedure has access to those variables Unlike local variables global variables are available to any procedure after they are declared and continue to exist until EASI itself terminates In previous versions of EASI a special statement called IMPORT was required in order for a global variable to be used within a procedure other than the one in which it was declared However the use of the IMPORT statement is no longer required and global variables are automatically available to all procedures If both a local and global variable have the same name then any references to that variable are considered by EASI to be references to the local version Hence access to the global variable of the same name will no longer be possible 52 PCI Geomatics Chapter 4 EASI Programming For example suppose a procedure declares two variables variable A is declared to be global and variable B is declared to be local The procedure is able to access and set both of these variables lobal integer A ocal integer B 1 2 A B Suppose next that this procedure calls a second procedure called Func2 call Func2 The new procedure Func2 will be able to access the global variable A since it was declared global but will be unable to access the variable B since it was declared local to the other procedure A 5
79. e not supported in EASI Example LOAD pci pro SHELL EAS 164 PCI Geomatics Chapter 8 EASI Language Reference LOCAL The LOCAL command declares EASI variables of the requested or default type in a manner similar to GLOBAL however with LOCAL the variables may only be accessed within the current function or procedure Local variables may also be implicitly declared by a LET command See the help provided under the LET command for further details LOCAL type name Carray_size type name Carray_size name names of EASI variables to declare type type of variable array_size number of entries in the array Possible types include byte a single unsigned byte char a single character 1 byte double an 8 byte double precision floating point value float a 4 byte floating point value integerCint a signed 4 byte integer mstring a multi line string array no arrays pointer ptr a generic memory pointer string an arbitrarily long string variable no arrays mvar modeling intermediate array Vertex a structure with an x y and z field GeoInfo a structure to hold projection information Example The following example declares a locally available array of integers with 256 elements called img_lut local integer img_lut 256 See Also GLOBAL LET EASI User s Guide 165 Commands Geolnfo The GeoInfo pre defined type is a structure for holding pro
80. ed class will contain all the data fields and methods belonging to the parent class which in turn may inherit some of these definitions from still another class The class being inherited from is called a base class for the new class For example consider the following definition for a class called Shape define class Shape ReadOnly double Centerx double Centery EndReadonly enddefine define method a Y on Shape this Centerx this CenterY enddefine y Using Shape as a base class the class Circle can be defined using inheritance as follows define class Circle inherits shape ReadOnly double Radius double Area EndReadonly enddefine define method SetRadius radius on Circle this Radius radius this Area 3 1415927 this Radius this Radius enddefine Since this new definition of class Circle inherits from class Shape the read only data fields CenterX and CenterY of Shape automatically become part of Circle Similarly the method SetCenter defined on Shape also becomes a method of Class Circle Hence this new definition of class Circle is equivalent to the earlier definition that did not use inheritance EASI User s Guide 123 Class Declarations An advantage of using inheritance is that a base class can be used to derive other similar classes all sharing some common behaviour providing a convenient way to reuse definitions and code For example another class called Rectangle could also build upon shape as
81. en DBPixels EASI User s Guide 195 Functions Table 5 DBReadArray DBReadgBinary DBReadChanDesc DBReadGeolInfo DBReadhHistory DBReadLUT DBReadLine DBReadMetaData DBReadPCT DBSegCreate DBSetChanInfo DBSync DBTransferInfo DBWriteArray DBWriteBinary DBWriteChanDesc DBWriteGeolnfo DBWriteHistory DBWriteLUT DBWriteLine DBWriteMetaData DBWritePCT DKClose DKOpen DKRead DKSize DKTruncate DKWrite Destroyldent EASIError EAlloc ECast EFree ERealloc F ASCII F CHAR F DATE FSERRNUM F EXTRACT F INPUT F LEN FSLOWCASE F PARDEF FSPARMAX FSPARMIN F PARTYP F SECS F STRING F TIME FSUPCASE 196 PCI Geomatics Chapter 8 EASI Language Reference Table 5 F VALUE FSVERSION FDDereference FDFilename FDFlags FDReference FDReferenceCount FDType FindSubString GetAsyncChar GetCWD GetDirectory GetEnv GetFileBasename GetFileExtension GetFreeDiskSpace GetGeolnfoParm GetLastErrorMessage GetLastErrorNumber GetMemory GetPID GetPathComponents GetRegistry GetRegistryPCl GetStat KillTask LicenseCheck MEMCopy MetaData Objects MkDirectory NETLink NETLinkOpen NETPort NETPortCreate NLSLookup NLSSetLocale NormalizePath ProgressCounter R
82. er number LET parm text string where parm is the name of a parameter The form used depends on the original definition of the parameter numeric or string and this does not change EASI will tell you if you use the wrong form and you can try again Remember a string parameter must be enclosed in double quotes EASI User s Guide 11 Displaying Parameters PRINT Type the following to the EASI prompt EASI gt LET VECTOR 2 3 5 6 4 EASI gt LET FUNCTION SQUARE For convenience you can omit the verb LET from any assignment statement This short form is easier to enter and simpler to read For example EASI gt VECTOR 2 3 5 6 4 EASI gt LET VECTOR 2 3 5 6 4 produce exactly the same result It is possible to allow a parameter to take the value s of another parameter The form of this assignment command is LET parml parm2 where parm1 parm2 are existing parameters of the same type Displaying Parameters PRINT The PRINT command allows procedures to print a line of information made up of numeric and or string expressions to the user s terminal Advanced options also allow direct cursor addressing limited graphics screen clearing and the changing of character attributes With this command elaborate menus and reports can be generated The general form of this command is PRINT expression expression where expression is of one of the following types 12 PCI Ge
83. es execution of the procedure currently running and returns control to the procedure that invoked it The calling procedure then resumes execution with the next statement This command has the form RETURN Cexpr where expr is an expression whose value can be given to the user when control is returned A RETURN statement can be placed anywhere in a procedure Example if STATUS DONE then EASI User s Guide 71 User Defined Functions return endif The RETURN statement is often used to return values from user defined functions See the section on user defined functions for further examples Stopping STOP The STOP command terminates all procedures and returns control to the user This is different from the RETURN command This command has the form STOP and can be placed anywhere in a procedure Example PRINT ERROR IN COMPUTATION STOP User Defined Functions As introduced earlier a function can be defined in EASI using the DEFINE keyword A function is a unit of EASI code typically designed to accomplish a specific task The body ofa function can contain any EASI commands A function definition appears within an EASI script file and an EASI script file may declare any number of functions Once declared a function is available for use by any other function or script regardless of which file the function was declared within A function definition includes specification of some numbe
84. f setting parameters required by a particular task running that task and so on to obtain the final result The example below is a listing of part of the ENHANCE EAS script in which the first step of the process is done namely the creation of a new database file The lines beginning with an exclamation mark are comment lines and are ignored by EASI as are blank lines ENHANCE EAS image resizing and enhancement Set parameters for the CIM task FILE Newname pix TEX1L Down sampled image TEX2 DBSZ 512 512 PXSZ 1 1 DBNC 1 DBLAYOUT BAND execute the CIM task RUN CIM In order to locate the script in order to execute it the script file must be located in the current working directory this is usually the same directory where EASI is started 22 PCI Geomatics Chapter 3 Developing Simple Scripts When the script is run EASI will execute the commands in ENHANCE EAS in order starting at the beginning of the file and ending when there are no more commands to execute at which time control will return to the EASI prompt Although the enhancement process is automated by the script their are still a number of deficiencies 1 The file names are hard coded into the script making it inconvenient to use 2 There is no on line help available 3 The script lacks any kind of error checking capability The remaining sections of this chapter will describe techniques
85. figuration of the command environment ALIAS or ALIAS token or ALIAS token alias string token The aliased token It must follow the usual rules for an identifier alias string The string to be substituted for the token The alias command has three forms The first is with no arguments and produces a list of the currently defined aliases The second takes one argument and reports the EASI User s Guide 137 Commands alias applied to the given token The third form is used to attach the specified alias string to the the token Thereafter when the token is the first item on an interactively entered command line the token will be replaced by the given alias string Example 1 This is a simple example is the following alias which replaces Is with system Is Thereafter typing ls in EASI would result in the ls command being passed to the operating system as ls system Is s The alias string can in fact take on a more complex syntax It is possible to have command line arguments substituted into the alias string Individual command lines arguments may be indicated by number i e 1 2 or 3 The set of all command line argument may be indicated as All command line arguments that are not explicitly referenced in the alias expansion are appended to the end of the resulting string Example 2 An example of using argument substitution is shown by the Is alias with all arguments also p
86. following is the completed ENHANCE script including built in on line documentation and status report In general EASI scripts should follow the same overall structure Note that while it is a great improvement over manually entering commands the ENHANCE script is still limited in that it follows a rigid linear control flow and lacks any error handling However capabilities such as control flow to produce more complex procedures and advanced error handling may be added using the more advanced features of EASI that will be introduced in later chapters ENHANCE EAS image resizing and enhancement DOC DOC ENHANCE DOC DOC Given an input file and channel number create a new DOC file containing a 512x512 sized copy of the input with DOC equalization enhancement applied DOC DOC 1 PARAMETERS DOC DOC ENHANCE requires the following input parameters DOC DOC Name Prompt Count Type DOC DOC INFILE Name of input file to be processed 1 64 Char DOC DBIC Database Input File Name 0 1 Int DOC OUTFILE Name of output file to be created 1 64 Char DOC DOC 2 INFILE DOC DOC The name of the input file from which data will be enhanced DOC DOC 2 DBIC DOC EASI User s Guide 35 The Entire ENHANCE EAS Script DOC The channel within the input file which is to be enhanced DOC DOC 2 OUTFILE DOC DOC The new file to create which will be of size 512x512 and DOC contain DOC a single channel with t
87. follows define class Rectangle inherits Shape ReadOnly double height double width double Area EndReadonly enddefine define method SetSize height width on Rectangle this Height height this width width this Area height width enddefine A newly created subclass may not redefine any data fields that have already been defined by its parent class nor can it change the access restrictions on data fields defined by the parent class Methods may however be defined on the new class with the same name as methods defined on the parent class In this case the new class will no longer be able to access the method of the same name belonging to its parent class Note Although a class may have one parent class multiple inheritance is not supported Initialization and Cleanup of Objects A pair of special methods called Initialize and Destroy may be defined on a class These two methods provide a way to automatically perform some processing whenever an object of 124 PCI Geomatics Chapter 7 Object Oriented Programming With EASI the class is created or destroyed and may be optionally defined for any class The Initialize method must be defined without any arguments If it has been defined for a class the Initialize method is executed automatically when an object of that particular class is allocated either when it is declared by a LOCAL or GLOBAL statement or by a call to the EAlloc intrinsic func
88. g a value to a variable E601 Undefined Identifier This indicates that a variable parameter or function was used that is not recognized Check the spelling of parameters or variables E602 Illegal Assignment This indicates that the target of an assignment the Ivalue is not legal Typically this occurs when assigning to a non existent variable or to a function E603 Can t Find Procedure Executable EASI User s Guide 203 Appendix A This indicates that the target of a RUN STATUS or CALL command could not be found E604 Internal Consistency Failure This error indicates an unexpected internal error This error should not occur in response to user mistakes E605 Subscript Out Of Range This occurs when entries in a numeric parameter or array are accessed that do not exist Array indices start at 1 E606 System Error This occurs when an operating system function fails unexpectedly E607 Syntax Error This error indicates that the user entered command line or command procedure could not be parsed Carefully review the provided input E608 Illegal Argument Value This normally indicates that an illegal argument value was passed to an intrinsic function E609 Bad File The requested file was not found or was corrupt E610 Task Terminated Aborted This error is generated when a PACE task terminates abnormally This can occur in response to a user error in establishing task parameters or if the ta
89. gram 1 EASI Program 260 DEF EX2 M EASI Example Program 2 EASI Program 270 DEF FUNCTION C Function SQUARE ROOT 280 DEF VECTOR N min max out Vector of Real Values 290 DEF POWER N min max out Power to Raise Values 206 PCI Geomatics Index A access data field 119 alias command 137 debug 151 argument function 74 variable list 78 array variable 44 ask command 24 139 B binary files as data files 83 bitmap variable 192 bitmap segments using 100 box expression 175 break debug 151 bye command 140 03 call command 140 case command 142 changing parameter 11 channel variable 190 class declaration 118 inheritance 122 cleanup object 125 command alias 137 ask 24 139 bye 140 call 140 case 142 debug 148 define 142 define class 145 define function 143 define method 147 define structure 144 delete 154 doc 155 enhance eas 31 eval 155 for 156 global 157 goto 158 help 159 import 161 input 162 log 167 model 98 169 parameter 7 print 12 23 172 printf 178 return 179 status 6 29 status_end 30 status_show 30 status_title 29 comments inserting 34 conditional statement 60 data field access 119 data file definition 81 data files binary files 83 207 Index text files 81 database files using 86 debug alias 151 break 151 command 148 declarat
90. he current shape define method Addvertex v on VLShape local int n n this numvertices 1 this vertices ERealloc vertex n this vertices this vertices n x this vertices n y this vertices n z NX X v v v call vECSetVertices this fd this layer this shape n this vertices EASI User s Guide 131 A Sample Class this numvertices n enddefine Using the VLShape Class The VLShape class provides a convenient and concise way to access data within a vector layer For example the following script checks the vertex lists of all the shapes and if the first and last vertex do not match it adds an extra vertex to the end of the list matching the first vertex thus ensuring each shape represents a closed area The height or z value of the vertices is ignored Note also that errors are trapped and the script ensures the file is correctly closed if an error does occur try local VLShape shape local Vertex v local integer n call shape Open irvine pix 25 w call shape FirstQ while Cshape AtEnd TRUE n shape numvertices if n gt O AND Cshape vertices 1 x l shape vertices n x OR shape vertices 1 y l shape vertices n y then v x shape vertices 1 x v y shape vertices 1 y call shape Addvertex v endif call shape Next endwhile call shape Close onerror call shape Close print getlasterrormessage call EASIError 800 Failed to clo
91. he enhanced by equalization input boc data DOC DOC 1 EXAMPLE DOC DOC Enhance the contents of channel 3 of a file called DOC input pix DOC creating and putting the results ina file called DOC output pix DOC DOC INFILE input pix DOC DBIC 3 DOC OUTFILE outfile pix DOC DOC RUN ENHANCE DOC_END STATUS_TITLE ENHANCE Image Resizing and Enhancement STATUS_SHOW INFILE 64 1 STATUS_SHOW DBIC 1 1 STATUS_SHOW OUTFILE 64 1 STATUS_END Set parameters for the CIM task FILE Newname pix TEX1L Down sampled image TEX2 DBSZ 512 512 PXSZ 1 1 DBNC DBLAYOUT BAND execute the CIM task RUN CIM Set parameters for the III task 36 PCI Geomatics Chapter 3 Developing Simple Scripts FILI Oldname pix FILO Newname pix DBIC already set by user DBOC 1 DBIW DBOW lexecute the III task RUN III Set the parameters for the FUN task to generate a look up table to enhance the image C use Equalization enhancement FILE FUNC DBIC DBLUT DBSN DBSD OSTR SDPT TRIM MASK DBHC Newname pix ce EQUA 1 Equalize Equalization enhancement execute the FUN task RUN FUN The fun task creates a data segment the number of which is recorded in the parameter LASC Set the parameters for the LUT task FILE Newname pix DBIC 1 DBLUT LASC DBOC 1 MASK
92. his number is not within the required range input Please enter a number between 1 and 25 NumberA endwhile print Thank You This WHILE loop makes sure that only a number that falls within a specified range from 1 to 25 is entered The user will keep being asked to enter numbers until the number entered satisfies the condition Once this happens the PRINT command that follows the ENDWHILE command will be executed Counted Loop FOR The EASI FOR command is similar to the WHILE looping function in that it also provides a general purpose looping construct However unlike the WHILE command which continues to loop until a criteria is met the FOR command will execute the statement list only a specific number of times The FOR statement generally has the following form for iter_var start_val TO end_val By incr_val statement list endfor EASI User s Guide 67 Procedure Control where iter_var is the iteration variable which may be any numeric variable type including a parameter start_val is the initial value to assign to the iter_var end_val is the value at which the iter_var will stop at when reached incr_val is the value by which to increment the iter_var at each iteration the default is 1 The FOR statement initializes the iteration variable to the initial value and then executes the statement list When the ENDFOR statement is reached the iteration variable is increased by the i
93. ically allocates and manages the memory storage for a string so that there is enough space to hold the value assigned Individual characters within the string may still be accessed using array style indexing as with arrays of characters name abcdefg print name 3 c An mstring is a multi line string which is a convenient way to represent textual data An mstring can be thought of as a list of strings which can grow to accommodate new strings being appended to it As with strings EASI manages the memory storage of an mstring allocating enough space to hold the assigned data An MSTRING initial contains no data When an initial value is assigned to the MSTRING it becomes the first string in the string list and is accessed using array style indexing with the index 1 EASI gt local mstring ListofNames EASI gt ListOfNames Alfred EASI gt print ListofNames Alfred EASI gt print ListofNames 1 Alfred 46 PCI Geomatics Chapter 4 EASI Programming A new strings can be appended to the end of an MSTRING by assigning it to the next available index For example a second string can be added to the list by assigning it to index 2 EASI gt ListOfNames 2 Betty EASI gt print ListoOfNames Alfred Betty More new strings can be added to the list and any of the previously assigned strings can be replaced with new values Charles Alexander EASI gt ListOfNames 3 EASI gt ListOfNames 1
94. ign is used to test for equality while inequality is tested with lt gt or Examples if name Frank then if size 0 then whileC flag lt gt 1 The operator is a regular expression matching test of equality for use between strings and tests whether the left side argument matches the right side regular expression Note that the string comparison is case insensitive and length of string matters Only multicharacter wildcard and single character wildcard operators are supported in the regular expression matching at this time Examples if filename pix then print Apparently filename is a PCIDSK file endif The gt lt gt and lt operations may only be performed on numeric expressions and perform in the expected way 188 PCI Geomatics Chapter 8 EASI Language Reference Examples while C total lt 100 while total lt 101 while NOT total gt 100 whileC NOT total gt 101 The logical operations AND and OR operate on two logical expressions while NOT operates on one logical expression The symbols amp and are considered to be equivalent to AND OR and NOT Examples if A 1 AND B 1 then endif if A 1 amp b 1 then endif Modelling Modelling expressions are similar to numeric expressions but have some special extensions and limitations The special extensions include the abi
95. ile Name DEFINE DBIC N 99999 99999 100000 Database Input Channel List Function The DEFINE command can be used to define new EASI functions which operate in a manner analogous to the predefined intrinsic functions These functions may take an arbitrary number of arguments and may optionally return a value DEF LINE FUNCTION function_name argl arg2 easi_command_list ENDDEFINE e g define function isprime a local max_div i max_div F INT a 0 5 1 EASI User s Guide 143 Commands Structure for i max_div 2 by 1 if a i FSINT a i return FALSE endfor return TRUE enddefine The arguments may be of any defined type The invocation of a user defined function is in many ways analogous to invoking anew EASI procedure file The function has a new variable scope but may access global variables declared by calling levels The advantage of user defined functions over separate procedure files is the ability to pass arguments and return values simplifying encapsulation See Also VarArgs AddShared The DEFINE command can be used to declare new complex data types consisting of named fields of various types DEF INE STRUCTURE structure_name fieldi_type fieldil_name Carray_size EN DD E FINE Once the define structure command has been parsed the named data type is available for use at any later time in the same EASI session The fields may be intrinsic types such a
96. ill be described throughout the remainder of this manual A complete list of intrinsic functions is available in the EASI reference section of the manual and in the on line help EASI Variables In addition to the parameters defined earlier EASI allows the definition of variables Variables differ from parameters in that they are not stored in an external file and hence do not remain defined between EASI sessions Variables may be defined to be of many different types including simple types like integers and aggregate types like structures The region of code in which a variable may be accessed is referred to as its scope EASI variables may be defined in one of two different scopes local and global The implications of using either or these scopes will be described in a later section A variable called a defined in a local scope can be declared interactively with the statement EASI gt local integer a Once declared the variable may be used EASI gt print a 0 When a variable is created it is normally given a default value The default value for an integer variable is 0 Variables can be assigned values EASI gt a 5 EASI gt print a 5 EASI User s Guide 41 EASI Variables Variables may also be used in assignments to other variables and also to parameters EASI gt local integer b EASI gt b a EASI gt print b 5 EASI gt DBIC a EASI gt print DBIC 5 Variables may also be used in expressions such a
97. ill be maintained however since the block may have moved other pointers referring to the same memory may no longer be valid and should be assumed to be invalid In the preceding example the second pointer pData2 may no longer point to a valid block of memory and should be either reassigned to pData or no longer used When a block of data is no longer required it should be released using the EFree intrinsic call EFree pData After being freed the block of data should no longer be referred to EASI User s Guide 51 EASI Variables Variable Scopes The scope of a variable is the region of code in which it is defined and can be used There are two types of scopes in EASI local and global The particular scope in which a variable exists depends on the way in which it is declared Local variables are declared with the LOCAL command and global variables with the GLOBAL command Local variables exist only while the procedure in which they were declared is being executed and may only be accessed within the procedure in which they were declared Each procedure has its own distinct local scope If a procedure is designed to access and run other procedures outside of its own programming the locally declared variables of the initial procedure will remain declared while the second procedure runs but will not be available to the second procedure Once any procedure completes returns all its local variables ar
98. image data built on top of GeoGateway a technology allowing access to data in many geomatics file formats in a uniform way A database is a grouping of data layers usually referring to a single file and can contain raster layers channels vector layers or segments look up tables and a variety of other auxiliary information A complete description of GeoGateway can be found in the manual GeoGateway Translations and Projections of particular interest is the section on the GeoGateway Data Model Note Not all file types support all of the possible capabilities If an unsupported operation is attempted on a file it will either be ignored cause the function to return a special value indicating the error or cause an EASI error to occur 86 PCI Geomatics Chapter 5 Working with Data Documentation on each of the EASI database access intrinsics is available in the reference manual To illustrate various techniques examples are presented here with detailed explanations Opening a Database File The first step in accessing the database file is to open it This is accomplished using the DBOpen intrinsic local int fd fd DBOpen irvine pix r if C fd 0 then print The file was not found return endif DBOpen returns an integer file handle on success or 0 if it fails to open the file As with the other file access intrinsics the file handle is used to access the file in all subseq
99. inates its local variables are lost and control EASI User s Guide 73 User Defined Functions returns to where the function was invoked from usually either another function or script or the EASI command line Loading and Executing Functions In order to use a function its definition must first be loaded into EASI If the function in the previous example is defined in a file called USERFUNC EAS then the LOAD command can be used as follows load USERFUNC EAS After it has been loaded the function may then be invoked using the CALL command call waitForUserResponse The empty brackets after the function name indicate the function requires no arguments Passing Arguments A function that requires arguments must declare the arguments in the define command The names given to the arguments are used to access the data within the body of the function Ten following simple function takes two arguments and prints the maximum value given define function PrintMax a b local integer Maximumvalue if a gt b then MaximumValue a else MaximumvValue b endif printf The maximum value is d n MaximumValue enddefine 74 PCI Geomatics Chapter 4 EASI Programming Once the function has been loaded it can be executed using the CALL statement as before this time specifying the arguments in brackets following the function name call PrintMax 3 7 When the function is executed
100. ing Functions A pair of intrinsic functions exist to allow an EASI function to cause an error condition to occur EASIError and ReCastEASIError The errors generated by these functions are identical to those raised by statements and intrinsics and are handled in the same way EASI Error The EASIError intrinsic function allows the user to raise an error specifying both a numeric error code and an error message which may be formatted using C style format specifiers The following are examples of the use of EASIError call EASIError 700 Invalid data call EASIError 701 File s is read only filename call EASIErrorc 702 In the last case where no message is specified a default message will be produced The range of numeric error codes from 700 899 is reserved for user applications and values in this range can be specified when using the EASIError function to raise new application specific errors Other standard error codes may also be used when the meaning is appropriate When an EASIError command is executed processing will continue in the same manner as if any error had occurred on the line containing the call to EASIError 110 PCI Geomatics Chapter 6 Error Handling ReCastEASIError The ReCastEASIError intrinsic function will cause the previous error to be triggered again This is typically used in conjunction with an error handler in the situation where an error was tr
101. ion class 118 default error 105 parameter 28 define command 142 define class command 145 define function command 143 define method command 147 define structure command 144 defining parameter 25 definition data files 81 expression 56 delete command 154 displaying parameter 12 doc command 155 documenting enhance eas 33 dynamic allocation pointer 49 E EASI help 8 introduction 1 OOP 117 overview 5 programming 39 script 21 system parameters 205 task 6 using 5 enhance eas command 31 documenting 33 script 35 error default 105 handling 105 information function 108 message 203 trap 106 error casting function 110 eval command 155 execute function 74 expression box 175 definition 56 format 173 logical 63 187 modelling 189 numeric 56 172 185 string 57 173 187 subscript 100 F for command 156 format expression 173 function argument 74 error casting 110 execute 74 loading 74 mathematic 194 member 121 user defined 72 functions defined 39 G geoinfo type definition 166 global command 157 goto command 158 statement 69 208 PCI Geomatics Index H handling error 105 help command 159 EASI 8 procedure 31 l if statement 160 import command 161 information function error 108 inheritance class 122 initialization object 124 input command 162 parameter 25 inserting comments 34 i
102. jection related information The define statement corresponding to it would appear as follows define structure GeoInfo charUnits 24 Map Units string at most 16 long doubleULX Upper left X coord georef units doubleULY Upper left Y coord georef units doubleLRX Lower right X coord georef units doubleLRY Lower right Y coord georef units doubleDEarth1l doubleDEarth2 doubleRefLong Reference Longitude doubleRefLat Reference Latitude double StdParallell double StdParallel2 double FalseEasting double FalseNorthing double Scale double Height double Longl double Latl double Long2 double Lat2 double Azimuth integer LandsatNum integer LandsatPath enddefine The most important field is the Units field which contains the map units string defining the georeferencing system For instance from irvine pix this would be UTM 11 S E000 The ULX ULY LRX and LRY fields are the positions of the upper left and lower right corners of the raster with which this projection information corresponds When the GeoInfo is related to a vector layer these will not be set to a meaningful value The remaining fields are special values used only for some of the complex projections Complex projections are those for 166 PCI Geomatics Chapter 8 EASI Language Reference which the map units string does not fully define the projection UTM SPCS and LONG are examples of simple projections defined fully by the Uni
103. label or line number GOTO commands can be used to escape or enter loops although this is poor style and may cause problems in future versions of EASI GOTO label 158 PCI Geomatics Chapter 8 EASI Language Reference label an existing line number or statement label Execution control is transferred to the statement at the label line number indicated Note that statement labels are indicated by an identifier at the beginning of a line followed by a colon and a statement If it is undesirable to place a statement on the same line for formatting purposes it may be placed on the next line and a backslash used to mark the split of the virtual line as shown in the example Example run cim onerror goto Error Error f print An error has occurred in creating the new database HELP The HELP command HELP H or prints online help for specified topic and subtopics The EASI online help facility is modeled after the VAX VMS online help command The topic defaults to the EASI PACE system help if a topic is not specified Up to 9 subtopics may be specified for a given topic In practice a maximum of 3 subtopics may exist for a topic Topic names must NOT be abbreviated but subtopic names can be abbreviated if they are unique HELP topic subtopicl subtopic2 subtopic3 The user can respond to the subtopic prompt by entering a subtopic if one exists or a command lt return gt or 1 l
104. lity to use channels in the expressions and a number of special modelling variables To understand the limitations of modelling expressions it can be helpful to realize that modelling expressions are evaluated in chunks over the whole requested region Each operation in the expression is done over a chunk taking zero or more blocks of image data as input and creating an output block of image data This means that modelling expressions cannot generally be used in place of numeric expressions unless the function treats modelling values specially EASI User s Guide 189 Expressions Channel Variables Nevertheless use of modelling expressions is fairly intuitive when used in simple assignment LET statements See Also Model Command Channels may be specified in a modelling expression using any of the following forms n Cx_expr y_expr n x_expr y_expr file spec n Cx_expr y_expr The first case is the channel sign followed by literal numeric value such as 1 2 or 3 indicating channel 1 2 or 3 of the implicit database The second example is similar but the channel number may be a numeric expression that is evaluated to be the channel number The third case is more general yet The file spec may be a database file name or a file handle returned by DBOpen and the channel number is evaluated as an expression Overriding the file modifies the database that the channel is assumed to exist on b
105. logging is not active to the terminal LOG DELETE The LOG DELETE command will terminate logging and delete the current log file If logging is not active the file EASI LOG will be deleted LOG string_expression The LOG command can be given an arbitrary string expression as an argument The contents of the string expression will be appended to the log file Log files record the things that occur in a session in such a way that the session can be reconstructed to some extent If the logfile is renamed as a EAS procedure it is possible to run the file and reinvoke the commands To some extent new macros can be created by recording user actions Other uses of the LOG commands are to record a session for debugging by PCI or other users and to record progress and timing for batch operations Example The following example records a couple of simpled steps into a EAS file so that it can be played back later as shown 190 start MYMACRO EAS e AMS AE ANS pix a cd log oun 168 PCI Geomatics Chapter 8 EASI Language Reference run mymacro MODEL The MODEL command is used to introduce a block of commands which are to be applied over an area of a database MODEL ON filespec OVER window_spec modeling_command_list ENDMODEL The filespec may be a database name or the handle returned by a previous DBOpen call The window spec specifies a subwindow of the database to operate on and is given in XOff
106. lower right corner at column 60 row 5 using a special graphics character set The BOX expression can be used to draw horizontal lines a box on only one row or vertical lines a box in only one column The BOXCLEAR expression is used to clear rectangular areas on most terminal types it is ignored on other terminal types The form of the expression is BOXCLEARCupperleftcol upperleftrow lowerr ightcol lowerrightrow Example PRINT BOXCLEAR 5 5 10 15 clears a rectangle with the upper left corner at column 5 row 5 and the lower right corner at column 10 row 15 using blank characters The PCILOGO expression is used to write out the PCI company logo on a CRT screen The logo is contained in a box 15 columns by 7 rows The quality of the logo depends on the terminal type The form of the expression is PCILOGO Cupperleftcol upperleftrow 176 PCI Geomatics Chapter 8 EASI Language Reference Carriage Return Suppression A Example PRINT PCILOGO 10 5 prints the PCI logo with its upper left corner at column 10 row 5 The character is used to leave the cursor at the end of the printed line rather than return it to the beginning of the next line This feature allows INPUT or ASK statements to request user input starting at any screen position The character must be the last character in the PRINT statement Note Any output EASI does is always to a new line Therefore the
107. luating to TRUE and the print statement to be executed A string expression can also be used to compare a string with a logical expression using the following operator e equals regular expression In this case the string on the right side of the operator is interpreted as a regular expression A regular expression is a way to represent a set of strings in a compact way using a pattern At the current time regular expressions in EASI only support single character wildcard matching using the character and multi character wildcard matching using the character For example the comparison in the statement if C filename set pix print success 64 PCI Geomatics Chapter 4 EASI Programming Logical Relations AND OR NOT will evaluate to true if filename matches the pattern set pix with any character substituted for the wildcard character such as set1 pix or set2 pix or seta pix However it will evaluate to false if filename is set pix or set10 pix or the empty string or any other string that doesn t match the pattern Similarly the comparison in the statement if C filename pix print success will evaluate to true of if the variable filename matches the pattern pix where any characters are substituted for the wildcard character such as test pix or even just pix in
108. lue That is any variables listed as an integer will recognize only whole numbers ie 0 2 47 If a numeric input for such a variable is not entered as a whole number for example if 3 999 is entered then the variable will only accept the value to the left of the decimal in this case 3 The number will not be rounded off On most platforms integers in the range 2 147 483 648 to 2 147 483 647 can be represented If a variable is declared as a double then the variable will represent real numbers with an 8 byte double precision floating point value for example 12 9 Numbers in the range 1008 to 107308 can be represented with 15 to 17 decimal digits of accuracy Similarly a float variable will represent real numbers with a 4 byte floating point value Numbers in the range 10 38 to 10 3 can be represented with 6 to 9 decimal digits of accuracy 1 The capitalization is for readability only numberoftableentries represents the same variable EASI User s Guide 43 EASI Variables Arrays A char or character variable will represent single characters such as A and 3 Finally a byte variable will represent only the integers from 0 to 255 Note that unlike parameters EASI variables represent single values and not vector values For example an EASI float variable represents a single number unlike an EASI numeric parameter which represents 16 numeric floating point values If a value is assigned to
109. mand generates a header title when the procedure is statused STATUS_TITLE text text is name of the task to appear in the header STATUS_TITLE generates a title using text as the task name for the header If the provided text is GEOREP and if a text parameter named GEOREP is defined EASI User s Guide 181 Commands STATUS TITLE will be used to add a descriptive message to the title Example status_title georep See Also STATUS SHOW STATUS STOP The STOP command stops execution and returns control to the user SYSTEM The SYSTEM command evaluates a string expression and passes it directly to the host operating system If the optional redirection is employed the results of the operating system command are assigned to the indicated MSTRING variable multi_var SYS TEM expn gt multi_var expn ove aring expression multi_var a variable of type MSTRING Example The following example is specific to Unix It will collect a list of names of pix files in the local directory and run CDL on them one after the other local mstring flist int i string dummy system Is pix gt flist for i 1 to F LEN flist file flist i run cdl input Hit lt Enter gt to continue dummy endfor 182 PCI Geomatics Chapter 8 EASI Language Reference TRY The TRY command provides a convenient syntax for trapping and handling errors within blocks of code It is typi
110. me of the file its access type the number 126 PCI Geomatics Chapter 7 Object Oriented Programming With EASI of the vector layer being accessed and various other information A field called AtEnd is used to indicate if there are any more shapes in the layer Since there is no boolean type in EASI AtEnd will be defined as a string variable and by convention will hold only the string values TRUE and FALSE define class VLShape ReadOnly string filename string access integer layer mstring fieldnames integer numfields integer shape string AtEnd Vertex ptr Vertices integer NumVertices EndReadonly Private integer fd EndPrivate enddefine Initialize and Destroy Methods The Initialize method will set default values to the fields in the class definition Note that by default EASI already sets numeric variables to 0 and string fields to empty define method Initialize on vLShape this AtEnd TRUE this fd 0 this filename this shape 1 this layer 0 this access this fieldnames enddefine The Destroy method will ensure that the file has been closed when the object is destroyed It will do this by simply calling the objects Close method The Destroy method also frees the list of vertices belonging to the shape EASI User s Guide 127 A Sample Class define method Destroy on vLShape call this close if this vertices NULL then call EF
111. method should take appropriate action based on the field and value being assigned Dynamic Field Methods in VLShape The GetDynamicField method will be used to access attributes fields in the current shape If a field reference is performed that doesn t refer to an actual field in the class VLShape then the GetDynamicField function will be invoked EASI User s Guide 133 A Sample Class automatically with the field name as its only argument The function will use that argument to search the list of field names kept in memory to determine the corresponding field number The field number can then be used to allow VECGetField to access the field value define method GetDynamicField field on VLShape if C this fd 0 then call EASTError 703 No Currently opened file endif local integer fieldnum fieldnum FindSubString this fieldnames field if fieldnum 1 OR field this fieldnames fieldnum call EASIError 701 Field s not found field endif then return VECGetField this fd this layer this shape fieldnum enddefine The SetDynamicField method operates in an analogous manner to GetDynamicField except it receives an extra argument containing the value to which the given field should be set define method SetDynamicField field value on VLShape if C this fd 0 then call EASTError 703 No Currently opened file endif if C this access lt gt w
112. n plist 3 plist 3 call Reproject gi go 2 plist printf ulx g uly g n plist 1 plist 2 printf 11x g lly g n plist 3 plist 3 The Reproject intrinsic may not be used to translate points from a projection to pixel line coordinates However this transformation is simple enough to perform directly using the information stored in the GeoInfo structure The following example converts the x and y coordinates in the first two elements of PLIST to pixel line local double xoffset yoffset xsize ysize xoffset gi ulx yoffset gi uly xsize gi Irx gi ulx DBPixles fd ysize gi Iry gi uly DBLinesC fd 94 PCI Geomatics Chapter 5 Working with Data plist 1 plist 2 C plist 1 xoff xsize C plist 2 yoff ysize Similarly a pixel line coordinate can be transformed to a projection as follows plist 1 plist 2 plist 1 xsize xoff plist 2 ysize yoff Finally note that it is possible to read and write separate projection information to vector layers in a database file for further details refer to the help for the intrinsic functions VecReadGeolnfo and VecWriteGeoInfo in the EASI reference manual or the on line help Vector Data The previous section focuses on working with raster data in a database file Some types of database files also contain vector data and the EASI database interface includes functions to access and manipulate vecto
113. n control will immediately be transferred to the statements after ONERROR After the error handling has been executed control continues with the next statement after the TRY ONERROR ENDONERROR clause Note that if an error occurs while executing the ONERROR block it is treated normally just as an error occurring immediately outside of the TRY statement For example the Invert function given above could be coded as follows using the TRY statement define function Invert x local integer y try y 1 x onerror print Invert the following error occurred print GetLastErrorMessage y endonerror return y enddefine Nested TRY statements It is possible to nest TRY statements within other TRY statements If an error occurs it will be handled by the innermost TRY statement that encompasses the offending line ofcode This allows general error handling blocks to be created for large sections of code while more specific error handlers can be used for important subsections of code GOTOs with TRY statements Certain uses of GOTO statements when using TRY style error handling can cause unexpected behaviour if care is not taken If 112 PCI Geomatics Chapter 6 Error Handling a GOTO statement is used to jump into the body of a TRY statement from outside of the TRY statement the ONERROR block will not be invoked if an error occurs Execution must flow naturally into a TRY statement for error handling to be pr
114. n in the form of commands which can be entered interactively at the EASI command line Examples of this type can be recognized as they are preceded by the standard EASI prompt EASI gt as follows EASI gt print Hi In this example the command entered to the right of the EASI prompt simply prints the message Hi Other examples given in the manual are in the form of commands which are part of an EASI script file These example differ from the interactive example above in that they are not preceded by an EASI prompt print Hi Sometimes the general syntax of a command is presented The syntax is given in a highlighted type face followed by a description of any special portions of the command Square brackets are used to indicate portions of the command syntax which are optional and ellipses are used to indicate portions of the command where a variable number of items can be put For example PRINT expression expression EASI User s Guide 3 Purpose of EASI where expression is of one of the following types e anumeric expression e a string expression This simplified example shows the syntax of the print command The brackets indicate that additional expressions to print can be given by separating them using commas Summary EASI is a powerful tool used for controlling the execution of tasks and for developing platform independent applications This manual desc
115. n statement is executed by EASI EASI User s Guide 55 Expressions Expressions Expressions are used to compute new values from data and can be composed of operators variables and parameters Expressions commonly appear on the right hand side of assignment statements and in argument lists to function calls Most expressions are classified as being either numeric logical also known as relational or string Brackets may be used in any type of expression to group sub expressions in order to ensure the are evaluated in the intended order Numeric Expressions Numeric expressions are formed using numeric elements and arithmetic operators The evaluation of the expression returns a single numeric value A numeric element can be any of the following e anumeric constant such as 3 14 e asubscripted numeric parameter such as VECTOR 2 e anumeric intrinsic function such as COS 0 5 e anumeric user defined function such as Average 4 6 from the earlier example e an EASI numeric variable of type byte integer float or double e asubscripted EASI numeric array variable Arithmetic operators specify the computation to be performed The operators are Multiplication Division Addition Subtraction Exponentiation gt 1 t N 56 PCI Geomatics Chapter 4 EASI Programming These are binary operators since each is used with two elements A subscripted numeric parameter or local numeric value m
116. name of the structure is specified immediately after the DEFINE STRUCTURE keywords in the example above the structure name is Point and the structure definition ends with the ENDDEFINE keyword The fields that make up the structure are given in the body of the structure definition After a structure has been defined variables may be declared of the new type LOCAL Point p The fields of the structure are accessed by appending a period oe 99 and the field name after the name of the structure variable 1 5 5 p x p y It is possible for structures to include arrays and other structures as fields DEFINE STRUCTURE Datasetinfo STRING Filename CHAR MapUnits 24 Point UpperLeft Point LowerRight ENDDEFINE LOCAL Datasetinfo Irvine 48 PCI Geomatics Chapter 4 EASI Programming Irvine Filname irvine pix Irvine MapUnits LONG LAT Irvine UpperLeft X 2342 233 Note here how the Filename field is a string and can hence be of any length but the MapUnits field is an array of chars and is limited in length to 24 characters Finally it is possible to declare arrays of structures LOCAL DatasetiInfo data 5 data 1 Filename testl pix data 2 Filename test2 pix EASI has some predefined structures Vertex and GeoInfo These structures are available for use in any program The Vertex structure represents a single three dimensional point and is eq
117. ncrement value or by 1 if using the default value The new value is then compared to the end value If this value is not exceeded the statement is executed again When the procedure has executed the required number of times the loop will stop and the program will continue on to the next command immediately following the EVDFOR command For example in the following program a FOR statement is used to repeat a calculation only a certain number of times specified by the user local double i NumberA Highest print This program will show a multiplication table for a given print number input Enter the multiplier number NumberA input Enter the highest number to show on the table Highest for i 0 TO Highest BY 1 print NumberaA i 7 NumberA endfor multiplied by Notice that the counting variable i needs to be declared in the LOCAL statement 68 PCI Geomatics Chapter 4 EASI Programming In the example Highest is the end value If 10 is entered as the highest number to be multiplied the procedure will run the calculation 10 times Each time 1 will increase BY one 1 Note that the increment value specified after the BY keyword in the FOR statement is set to 1 but since 1 is also the default increment value its specification may be omitted A for loop can by made to count by two s by specifying BY 2 or to count backwards by specifying BY 1 A For loop ma
118. ndicate that logging was stopped the following message is entered into the log file just before closing HH MM SS LOG STOPPED DD MMM YY If the log file is already closed this command is ignored Entering A Log Message To force a message into the log file type LOG message This will create the following entry in the log file without a time stamp message If logging is not enabled this command is ignored Examining The Log To list the log file to your terminal type EASI gt LOG LIST The entire log file will be sent to your screen for review As the log file can be very long you should use this command with caution The log file can be either open or closed when you execute this command Starting A New Log File To start a new log file first delete the old log file using instruction EASI User s Guide 17 When You Are Finished EASI gt LOG DELETE This deletes the old log file if it existed A new file will be created when you start logging again Example Logging Session EASI gt LOG DELETE EASI gt LOG START EASI gt LOG Example log message EASI gt LOG STOP EASI gt LOG LIST 13 15 02 LOG STARTED 30 FEB 83 Example log message 13 15 30 LOG STOPPED 30 FEB 83 When You Are Finished Summary Once you have completed your work and you wish to leave your terminal you can exit EASI using the BYE or EXIT commands These two commands are identical in function Type EASI gt BYE Yo
119. nhanced by equalization input data DOC EASI User s Guide 33 Commenting Procedures REM DOC 1 EXAMPLE DOC DOC Enhance the contents of channel 3 of a file called input pix DOC creating and putting the results ina file called output pix DOC DOC INFILE input pix DOC DBIC 3 DOC OUTFILE outfile pix DOC DOC RUN ENHANCE DOC_END With the documentation added the user of the ENHANCE script will be able to easily get help on the usage of the script using the HELP command EASI gt help enhance Commenting Procedures REM It is considered good technique to include comments and programming notations in with your procedures These comments remarks can be included by first placing a command marker at the start of the line as shown in the following example oy Comments and program notes are placed here The symbol is a short cut instead of typing the long form of the command marker the REM command For example REM Comments and program notes are placed here Once EASI encounters a or a REM it will ignore the rest of that input line Remark lines have no effect on a procedure s execution Text following a or REM marker need not be enclosed in double quotes Comments must appear on lines by themselves and cannot appear on a line following a command 34 PCI Geomatics Chapter 3 Developing Simple Scripts The Entire ENHANCE EAS Script The
120. ntroduction EASI 1 L loading function 74 log command 167 record 15 logical expression 63 187 loop for statement 67 M mathematic function 194 member function 121 message error 203 model command 98 169 modelling expression 189 N name variable 42 notes reserved words 200 setup file 200 syntax 199 numeric expression 56 172 185 parameter 9 oO object cleanup 125 initialization 124 OOP EASI 117 overview 117 overview EASI 5 OOP 117 P parameter changing 11 commands 7 default 28 defining 25 displaying 12 enhance eas 27 input 25 numeric 9 search 14 set 13 setting 11 string 10 subscribed 10 pointer dynamic allocation 49 print command 12 23 172 printf command 178 procedure help 31 run 14 status report 29 programming EASI 39 projections 209 Index using 92 R record log 15 reserved words notes 200 return command 179 statement 71 value 77 run procedure 14 S scope variable 52 scope rule variable 53 script EASI 21 enhance eas 35 using 23 scripts defined 39 search parameter 14 set parameter 13 setting parameter 11 setup file notes 200 special variable 193 special type variable 45 special variable using 101 statement conditional 60 goto 69 if 160 loop for 67 loop while 66 return 71 stop 72 status command 6 29 status report procedu
121. o 1023 As x and y value from 0 to 511 the expression x 2 1 varies from 1 to 1023 There are limits on the complexity of the subscript expressions The MODEL command is implemented in such a way that chunks of the database are operated one at a time and the subscripts area evaluated only at the corners of each chunk As long as the subscript expressions are linear in x and y this is equivalent but if non linear expressions or bi variate expressions are used then the results will not be that which is expected These limitations represent an area of research and they may be relaxed at a latter time It is also legal for the subscript expressions to extend of the source database In this case image values from the edge of the database are replicated out as far as is need to satisfy requests Thus a simple filter such as the following will work in a reasonable manner even on the edge of the database EASI User s Guide 191 Expressions Bitmap Variables MODEL 7 4 x 1 y 1 4 x y 1 4 x 1 y 1 4 x 1 y 4 x y 4 x 1 y 4 0x 1 y 1 4 x y 1 4 x 1 y 1 9 ENDMODEL Bitmaps or graphic planes are a form of one bit deep image primarily used to serve as masks for regions where operations are to take place and may be specified in a manner very similar to image channels All the rules previously indicated for image channels also apply to bitmap layers except that the
122. o f len varargs if varargs i gt MaximumValue then MaximumValue varargs i endif endfor return Maximumvalue enddefine The vmax function must be called with at least two and an arbitrarily large number of arguments EASI User s Guide 79 User Defined Functions 80 PCI Geomatics Working with Data Text Files EASI provides a number of functions that provide the ability to access and manipulate a large variety of image data and image related information This includes the ability to directly access raster imagery bitmaps look up tables vector segments and projection information Using these functions powerful applications can be quickly and conveniently built Access to text files is available through the use of the TextOpen TextClose TextRead and TextWrite Intrinsic Functions Access to a textfile is initiated using TextOpen This function takes the filename and an access specifier and returns a file handle The file handle is an integer which is associated by EASI with the open file and is used in all subsequent access to that file until it is closed The access specifiers may be either r for read only access to the file w for write access to the file or a for append access to the file EASI User s Guide 81 Text Files For example to open an already existing text file called data txt local integer fd fd TextOpen data txt
123. o trap errors Since a call to DBOpen returns a value of 0 if the file could not be opened instead of raising an EASI error an explicit call to EASIError is made This allows the TRY statement to handle the error just as any other Since the error will never propagate out of the function no error message is required The Close method will close the file if one is open define method Close on VLShape if this fd 0 then call DBClose Cthis fd this fd 0 endif enddefine First and Next Methods The First and Next methods are used to iterate between shapes within a vector layer Both of these methods simply call the VECNextShape intrinsic appropriately and store the result in the field shape In addition if there are no more shapes the variable AtEnd is set to TRUE The GetVertices method is used to read the vertex list of the first shape define method First on VLShape if C this fd 0 then EASI User s Guide 129 A Sample Class call EASIError 703 No Currently open file endif this shape VECNextShape this fd this layer 1 if C this shape 1 then this AtEnd TRUE call this Clearvertices else this AtEnd FALSE call this Getvertices endif enddefine The definition of Next is very similar define method Next on vLShape if C this fd 0 then call EASIError 703 No Currently opened file endif this shape VECNextShape thi
124. of a database The basic syntax of the MODEL commands is MODEL ON filespec OVER window_spec model ling_command_list ENDMODEL The filespec may be a database name or the handle returned by a previous DBOpen call The window _spec specifies a subwindow of the database to operate on and is given in XOff YOff XSize YSize format The modelling command _list can be any of a variety of commands The most important command that can be applied in a model is a modelling assignment This is a normal assignment LET statement using database channel specifiers for assigned to and source values Using Image Channels An example of a simple modelling command to set channel one of a file to the value zero is model on irvine pix 98 PCI Geomatics Chapter 5 Working with Data 1 0 endmodel As shown in this example a channel is specified using the special symbol Similarly to set the first channel to the sum of the second and third channels the command 1 2 3 can be used within the body of the model command It is also possible to use variables or even expressions that evaluate channel numbers in a modelling expression To do this curly braces are used around the expression that specifies the channel i i 1 i 2 All of the channels being referred to in the modelling expression must exist on the file referred to in the MODEL command however it is possible to s
125. of the image the edge pixels are copied outward and used instead This allows filters to be created and used which can be applied over an entire image including the edges The subscript expressions used must be linear and uni variate When no subscript expression is given it is equivalent to the specification x y Using Bitmap Segments In addition to image channels bitmap segments may also be accessed by modelling expressions The specification of a bitmap is exactly the same as of a channel except that the special symbol is used The following example will clear any pixels in a database channel that are not under a mask where the mask is a bitmap segment in database segment 5 1 1 5 Each point in a bitmap may only have the values one or zero the assignment of any non zero value to a bitmap is treated as setting the bitmap pixel to one 100 PCI Geomatics Chapter 5 Working with Data Filtering Example Special Variables A number of special variables are available within an EASI model region These variables may not be assigned to but rather are set to appropriate values by EASI and are available for use within the model Table 4 Special Modelling Variables and Descriptions x current x pixel processing location y current y line processing location dbx size of database in x pixel direction dby size of database in y line direction meterx size of
126. omatics Chapter 2 Using EASI e anumeric expression e a string expression e a format expression e a BOX or BOXCLEAR expression Example PRINT The square of 4 1 is 4 1 4 1 oe 99 Use of a comma on a print line as shown in the example above denotes a separation between various print expressions In this way various print expressions may be intermixed Examining Parameter Sets STATUS There will be perhaps hundreds of parameters in the parameter file and each procedure will likely use a different subset of these You can examine the parameters for a procedure without running the procedure itself by issuing the STATUS command STATUS proc where proc is the name of a procedure Type EASI gt STATUS EX1 Your screen will clear and the following will appear EX1 Example Task 1 EASI V5 2 HH MM DD MMM YY FUNCTION Function to Perform ROOT SQUARE SQUARE VECTOR Vector of Real values gt 2 3 6 4 The first line gives a short description of the program the current software version and the time and date Following this EASI User s Guide 13 Searching For Parameter Names SEE is a list of parameters needed to run EX1 and their current values Type EASI gt VECTOR 4 EASI gt STATUS EX1 Notice that the FUNCTION parameter was unchanged while VECTOR is different STATUS does not change the parameters it is simply an aid that frees you from memorizing the parameters used
127. omponents with one or more operators Operators specify computations to be performed using the values of the basic components to obtain a single value EASI User s Guide 185 Expressions Numeric Numeric expression in EASI are normally operated on in double precision floating point Values with less precision are promoted to double precision before operations are performed A wide set of built in operations are available in numeric expressions They are listed below accompanied by a short description Addition Subtraction b b i Multiplication b Division Exponentiation Parenthesis also square ckets LOonvwonnyn wo MY sr x Unary negation A numeric element can be any of the following e A numeric constant e An EASI variable of type byte int float or double e An element of a numeric variable array e A numeric intrinsic function e A numeric user defined function e A subscripted numeric parameter Numeric constants can be entered as decimal or scientific notation numbers with an optional negative sign Scientific notation is denoted with the E or D character as show below Example print 1 23e5 12300 1 23 10 A 5 See Also Intrinsics 186 PCI Geomatics Chapter 8 EASI Language Reference String String expressions in EASI are performed upon arrays of characters with a known but unlimited length The only built in operation supported for string expression
128. on how to specify input values for scripts and to create on line documentation Error handling will be left to a separate chapter A complete version of the simple ENHANCE script will be presented at the end of this chapter Interaction With Procedures A script will typically need to input some data on which to act It will also need some way to output its results Information can be written to the screen using the PRINT command and input data can be specified either interactively using the ASK command or by using parameters combined with the STATUS command Printing a Line PRINT The PRINT command allows procedures to print a line of information made up of numeric and or string expressions to the user s terminal Advanced options also allow direct cursor addressing limited graphics screen clearing and the changing EASI User s Guide 23 Interaction With Procedures of character attributes With this command elaborate menus and reports can be generated The general form of this command is PRINT expression expression where expression is of one of the following types e anumeric expression e a string expression e a format expression e a BOX or BOXCLEAR expression Examples print The square of 4 1 is 4 1 4 1 print DBIC DBIC 66 99 Use of a comma on a print line as shown in the example above denotes a separation between various print expressions In this way various
129. ooping construct over a series of numeric values FOR iter_var start_val TO end_val BY incr_val f statement_list ENDFOR iter_var The iteration variable This may be any numeric variable type including a parameter start_val This initial value to assign to the iter_var end_val when iter_var passes this value iteration stops incr_val Value by which to increment iter_var each i iteration The default is Ih The FOR statement initializes the iteration variable to the initial value checks it against the end value and if the end value is not exceeded it executes the statement list When the ENDFOR statement is reached the iteration variable is incremented by the increment value and compared to the end value If the end value is not exceeded the statement list is executed again 156 PCI Geomatics Chapter 8 EASI Language Reference The start value may be greater than the end value and the increment value may be negative but if the increment value does not take the iteration variable value closer to the end value each iteration the FOR loop will never terminate It is possible to alter the value of the iteration variable inside the FOR loop and also to use GOTO s to escape or enter the loop but this is poor style and may cause problems in future versions of EASI Example The following example runs the PACE task CLR on the first 128 channels of the PCIDSK file hyper1l pix
130. operly initialized by EASI Similarly if a GOTO statement is used to jump outside of a TRY block from with the TRY block a subsequent error in the same procedure or function will still cause the ONERROR block to be invoked Execution must flow naturally out of a TRY block for the error handling to be properly disabled by EASI In general GOTO statements should not be used to enter or exit TRY statements Error Handling Example Suppose a user needs direct access to the data within a database channel The following function does all the work in opening and closing the file allocating sufficient memory and reading the file The function could fail for a variety of reasons such as the file doesn t exist the specified channel does not exist or failure to allocate sufficient memory To handle possible failures the function uses a TRY block to do the work and executes clean up code in the corresponding ONERROR block function to read an entire database channel into a float buffer and return a pointer to that buffer DEFINE FUNCTION ReadChannel filename channel TRY local integer fd error i local float ptr buffer fd DBOpen filename r if C fd 0 then call EASIError 700 EASI User s Guide 113 Trapping Errors in Blocks of Code endif buffer EAlloc float DBPixels fd DBLines fd for i 0 to DBLines fd 1 call DBReadLine fd channel i O DBPixels fd buffer i DBPixels fd
131. or ENDIF ENDONERROR return frequency ENDDEFINE See Also FSERRNUM UNDEFINE The UNDEFINE command removes a parameter from the parameter file UNDEFINE parm parm name of a parameter Example undefine file WHILE The EASI WHILE command provides a general purpose looping construct WHILEC log_expr_ statement_list ENDWHILE log_expr a logical expression which is evaluated before 184 PCI Geomatics Chapter 8 EASI Language Reference each iteration of the loop The logical expression in the WHILE statement is evaluated and if the result is true the statement list is executed otherwise control skips to the statement following the ENDWHILE After the statement list has been executed control returns to the WHILE statement to test the logical expression again It is possible to jump into or out of the WHILE loop using the GOTO statement but this is poor style and may not work in future versions of EASI Example The following example prompts the user for a yes or no answer to a question and continues prompting until an acceptable answer is given local string answer input Enter lt Yes gt to proceed or lt No gt to abort answer while answer yes amp answer no input Please answer either lt Yes gt or lt No gt answer endwhile Expressions An expression represents a single value It can be a single basic component such as a constant or a combination of basic c
132. or Database Input Channel Notice here a special abbreviation of 6699 the print command is used the single letter p EASI gt p DBIC 1 Parameters can be modified by assigning values to them EASI gt FILE irvine pix EASI gt FILE irvine pix Con Windows NT systems EASI gt DBIC 1 2 String parameters like FILE are assigned values by putting the value in quotes Note that on Windows NT systems the double quotes have a special meaning so a different format is required to achieve the same ends Numeric parameters like DBIC are assigned values by listing these values separated by commas After the parameters for a given task have been set the task can be run EASI gt r CDL Here the abbreviation r is used for the RUN command A task will typically produce output to the screen or to data files located on disk To exit EASI use the command QUIT EASI gt quit EASI User s Guide 7 Getting Help HELP Getting Help HELP EASI provides extensive on line help documentation Typing HELP or followed by the name of a subject will put you into the on line help system of EASI To exit the on line help press lt cr gt until the usual EASI gt prompt reappears Try typing EASI gt HELP or EASI gt This will display general help information on the screen Typing HELP EASI displays information about EASI Typing HELP HELP shows information about the EASI on line hel
133. p feature Help topics often have subtopics associated with them You can access these subtopics directly by typing the subtopic name after the topic For example type EASI gt HELP EASI COMMANDS LET This will display information about the LET command subtopic If the topic you choose has subtopics you will see a list of those subtopics at the end of the help information For example if you started the help feature by typing HELP EASI the following prompt would appear at the end of the help text for the EASI topic Subtopics Commands Expression Functions Notes EASI Subtopic 8 PCI Geomatics Chapter 2 Using EASI In this case there are 4 subtopics available to you Commands Expression Functions and Notes The first word of the prompt is the name of your current topic EASI in this example You can now choose a subtopic from the list in the help text by typing either its full name or the first few letters of its name which distinguish it from the other subtopics on the list For example EASI Subtopic COM This will display the list of EASI commands Each of these commands is a subtopic and one of them may be entered to see the specific help about that command You have several other options when prompted to choose a subtopic To review the information on the current topic type a question mark If you are currently looking at the help of a subtopic pressing lt cr gt carriage return steps you ba
134. pecify channels in different files In this case the file specifier of an open file needs to be given in addition to the channel number within the braces The following example copies channel 1 of the file file pix to the file irvine pix local int fd fd DBOpen file pix r model on irvine pix 1 fd 1 endmodel call DBCloseC fd When multiple files are being used the window on which the operation is performed is the window corresponding to the default file that is the file specified in the MODEL command Since no window has been specified in the previous example the entire database size of irvine pix is used If irvine pix has a size of 512 pixels 512 lines and file pix has size 1024 pixels by 1024 lines only the 512 by 512 subwindow in the top left corner of file pix will be copied EASI User s Guide 99 Data Modelling Subscript Expressions A simple subscript expression may be given along with each channel specification to change the pixels being accessed These expressions are given in square brackets after the channel specification and use the special symbols x and y to represent the particular pixel and line locations when the expression is evaluated for each point For example the following modelling expression will shift image channl 1 upwards by one pixel 1 1 x y 1 If the modelling expression refers to a pixel outside
135. processed Parameters come in two forms string text and numeric numbers Parameters are stored in a file in the local working directory so they retain their values between EASI sessions Tasks are individual programs designed to accomplish specific jobs For example there is a run task to run or execute a program To create a local working copy of the master parameter file run the COPPRM task as shown At the end of the line press the carriage return lt cr gt Enter EASI gt run copprm EASI is not case sensitive Commands can be entered in upper lower or mixed case To view the parameters that a specific task requires use the STATUS command EASI gt status CDL The status command will display parameters required by a task along with their descriptions and current values If a parameter is not yet set but is required in order for a task to run it will be marked as MISSING CDL Channel Descriptor Listing V7 0 EAST PACE FILE Database File Name irvine pix DBCL Database Channel List DTYP Description Type SHORT FULL SHORT REPORT Report Mode TERM OFF filename TERM 6 PCI Geomatics Chapter 2 Using EASI To view the value of a single parameter use the PRINT command EASI gt print file irvine pix This displays the contents of the predefined string parameter FILE to the screen There are many predefined parameters An example of a numeric parameter is DBIC which stands f
136. r information Vector data is stored in a segment or layer within a database file Each segment containing vector data is referred to as a vector layer Each vector layer contains some number of shapes possibly zero where a shape is a structure containing a list of points and a set of attribute information An attribute is a named field of a particular type such as string integer or float A shape may have any number of attributes associated with it but all the shapes within a given layer must have the same number and types of attributes The following examples illustrate techniques used to access vector data The first step is to open the file containing the data local int fd fd DBOpen irvine pix r EASI User s Guide 95 Vector Data Given that a segment number stored in the integer variable layer exists access to the shapes within the layer is accomplished using the VECNextShape intrinsic This intrinsic returns the integer identifier associated with a shape Each shape is accessed using a unique integer identifier called a shape ID No assumptions should be made about the numbering of these identifiers In particular it should not be assumed that the shape IDs are numbered in the sequence 1 2 3 since vector operations may result in an irregular though valid numbering The identifier associated with the first shape is given by VECNextShape when called with the value 1 as its thi
137. r of arguments which are values passed to the function when it is 72 PCI Geomatics Chapter 4 EASI Programming invoked A function may optionally return a value using the RETURN command The syntax for a function definition is DEFINE FUNCTION function_name argl arg2 A easi_command_list ENDDEFINE where function_name is a unique name given to the function following the same rules as variable names That is functions names must begin with a letter a z and followed by any number of letters digits 0 9 and underscore characters _ argl arg2 argN are a list of argument names There may be any number of arguments or no arguments It is also possible to specify a variable number of arguments easi_command_list is the body of the function comprised of any number of EASI commands The following is an example of a very simple function requiring no arguments and which does not return any value It can be used to temporarily halt the execution of a script define function waitForUserResponse local string InputvValue input Please press enter to continue Inputvalue enddefine The function prints a prompt to the screen using the INPUT command and waits for the user to press the enter key Any input the user types is stored in the local string variable InputValue but since this value is not needed it is never used When execution reaches the end of a function definition the function term
138. rd argument and the identifier associated with subsequent shapes can be obtained using VECNextShape called with the shape ID of the previous shape as the third argument There are no more shapes when the shape ID returned by VECNextShape is 1 The following example loops over all the shapes in a vector layer and prints the number of vertices belonging to each shape using the VECGetVertices intrinsic function local integer shape shape VECNextShape fd layer 1 while shape 1 printf Shape d has d vertices n shape VECGetVertices fd layer shape shape VECNextShape fd layer shape endwhile The number of attribute fields that each shape in the layer has is obtained using the intrinsic VECGetFieldCount Attribute fields are referred to by number from to the number of fields in the layer The name of each attribute field is obtained using VECGetFieldName 96 PCI Geomatics Chapter 5 Working with Data The following code prints the names of each of the attributes in the layer local integer NumberofAttributeFields attribute NumberofAttributeFields VECGetFieldcount fd layer for attribute 1 to NumberofAttributeFields print VECGetFieldName fd layer attribute endfor The actual value in an attribute field for a given shape is obtained using the VECGetField intrinsic function The next piece of code prints the attribute names and values for each of the
139. re 29 status_end command 30 status_show command 30 status_title command 29 stop statement 72 string expression 57 173 187 parameter 10 strings using 83 structure variable 47 subscribed parameter 10 subscript expression 100 syntax notes 199 system parameters EASI 205 T task EASI 6 text files as data files 81 trap error 106 type variable 43 type definition geoinfo 166 U user defined function 72 using bitmap segments 100 database files 86 EASI 5 projections 92 scripts 23 special variable 101 strings 83 vector data 95 210 PCI Geomatics Index vV scope 52 value scope rule 53 return 77 special 193 variable special type 45 array 44 structure 47 bitmap 192 type 43 channel 190 variable list declaration 54 argument 78 defined 41 vector data name 42 using 95 211 Index 212 PCI Geomatics
140. ree this Vertices this Vvertices NULL endif enddefine Open and Close Methods The Open method of class VLShape will be used to open a file and set it to a vector layer The method will be defined to take a variable number of arguments as indicated by the VARARGS keyword either two or three The first two arguments will be the file name and layer number respectively The third argument if given will be the access specifier Ifa third argument is not given read only access will be initiated define method Open filename layer varargs on VLShape try determine file access local string access if cree er arse 0 then access else access varargs 1 endif attempt to open the file this fd DBOpen filename access if Cthis fd 0 call EASTError 700 this filename filename this access access this layer layer Initialize shape id to the first shape in the layer call this FirstQ read the number of fields and the fieldnames this numfields VEcGetFieldcount this fd this layer local integer i 128 PCI Geomatics Chapter 7 Object Oriented Programming With EASI for i 1 to this numfields this fieldnames i VECGetFieldName this fd this layer i endfor onerror if an error occurred close the file call this cClose call EASIError 700 File could not be opened endonerror enddefine Observe that the body of the Open method is enclosed in a TRY statement t
141. ribes the capabilities of EASI giving examples where appropriate to illustrate important features and techniques Complete reference documentation is also included Although not intended as a general introduction to programming nor as a specific aide to any particular application domain this manual provides the in depth understanding required by an EASI user to take full advantage of its features and capabilities PCI Geomatics Using EASI This chapter is directed to users with little or no knowledge of PCI s EASI software By the end of this chapter you will have gained enough knowledge to use EASI as a command environment to set up and execute tasks and to be able to obtain help using the on line help system Overview of Using EASI This chapter and the rest of the manual assumes that EASI has been successfully installed and setup on your system Once setup EASI may be invoked from a command line by typing the command easi prompt gt easi In some situations EASI may also be invoked by clicking the EAST icon Once EASI is running an EASI prompt will appear EASI gt Commands are entered interactively at this prompt for two main purposes 1 To manipulate parameters EASI User s Guide Overview of Using EASI 2 To execute tasks Parameters are special variables that control the execution of tasks For example the DBIC parameter allows you to specify which image channel contains the data to be
142. s char or float or may be String or MString or other complex structures defined using the DEFINE STRUCTURE command however structure fields may not be of type gt MVar Note An array size specifier should not be used if the field is of type String or MString 144 PCI Geomatics Chapter 8 EASI Language Reference Example Define a structure to hold information about a file create a variable of the new type and assign values to it DEFINE STRUCTURE Datasetinfo char Filename 128 char Mapunits 24 double ULX double ULY double LRX double LRY int HasRasterData int HasVectorData ENDDEFINE LOCAL DatasetInfo DSInfo DSInfo Filename file DSInfo MapUnits LONG LAT DSInfo ULX 12 5 DSInfo ULY 45 0 DSInfo LRX 13 0 DSInfo LRY 44 5 DSInfo HasRasterData 0 DSInfo HasVectorData 1 Class The DEFINE command can be used to declare new object classes Defining a class is similar to defining a structure except that a class can have special functions called methods associated only with objects variables of that class Classes also support data hiding for data fields DEF LINE CLASS new_class_name INHERITS base_class_name fieldil_type fieldil_name Carray_sizel field2_type field2_name Carray_size2 Readonly fieldn_type fieldn_name Carray_sizen EASI User s Guide 145 Commands EndReadonly Private fieldm_type fieldm_name C
143. s addition EASI gt a a b 1 EASI gt print a 11 Further details on expressions will be given in a later section Variable Names Variables names are comprised of the letters A Z the numbers 1 9 and the underscore character _ The first character of the variable name must always be a letter As with the rest of EASI variable names are not case sensitive so for example variables named delta DELTA Delta will all be considered to be the same Variable names may be arbitrarily long It is illegal to declare variables with the names of certain EASI keywords that is certain words that have special meaning to the language For example a variable may not be called RUN since RUN is an EASI command Attempting to define a variable with such an illegal name will result in EASI generating an error The following are some valid variable names i amount file_name x2 NumberofTableEntriest 42 PCI Geomatics Chapter 4 EASI Programming Variable Types There are five basic types of variables available in EASI Table 1 Variable Types and Descriptions Integer 4 byte signed integer number Float 4 byte single precision floating point number Double 8 byte double precision floating point number Char single character 1 byte Byte single unsigned byte Integer 4 byte signed integer number A variable of type integer can represent a signed four byte integer va
144. s fd this layer this shape if C this shape 1 then this AtEnd TRUE call this clearvertices else this AtEnd FALSE call this Getvertices endif enddefine Vertex Access Methods The list of vertices for the current shape is maintained in the field Vertices The ClearVertices method sets the vertex list for the current shape to empty define method Clearvertices on VLShape if this vertices NULL then call EFree this vertices this vertices NULL this numvertices 0 if C this shape 1 then call veECcSetVertices this fd this layer this shape 0 this vertices 130 PCI Geomatics Chapter 7 Object Oriented Programming With EASI endif endif enddefine The GetVertices method reads the vertex list for the current shape into memory define method GetVertices on VLShape local Vertex ptr v if this vertices NULL then call EFree this vertices this vertices NULL endif if this AtEnd TRUE then v vECGetVertices this fd this layer this shape this numvertices f len v this vertices v endif enddefine The SetVertices method sets the list of vertices for the current shape to a given vertex list define method SetVertices num vertices on VLShape call veECSetVertices this fd this layer this shape num vertices call this GetvVvertices enddefine The AddVertex function adds a single vertex to the list of vertices belonging to t
145. s is the concatenation operation which is denoted with a sign String variables can be subscripted to return a string value consisting of only one character A string element can be any of the following e A string constant enclosed in double quotes e An EASI variable of type string e A subscripted EASI variable of type string e A subscripted variable of type mline e A string intrinsic function e A string user defined function e A string parameter String constants are enclosed in double quotes and may include additional quotes if they are escaped with back slashes String constants can not span lines and do not require a closing quote if they are the last item on a line Example local string s s Hello world s Hello world s Hello world See Also Intrinsics Logical Logical expressions in EASI are used to compute TRUE FALSE results for use with the IF and WHILE conditional EASI User s Guide 187 Expressions statements There is currently no way to store a pure logical value in an EASI variable Logical expressions consist of comparisons between numeric and string expressions combined with the use of the logical operations AND OR and NOT The equality and inequality tests may be used with either two numeric expressions or two string expressions When comparing two strings the shorter is temporarily padded out with spaces and the comparison is case insensitive The equal s
146. s to ensure that the meaning of the test is clear if C Ca 1 AND b 2 OR a 2 AND b 1 print success In this case either a must equal 1 and b must equal 2 or alternatively a must equal 2 and b must equal 1 for the logical expression to evaluate to TRUE and success to be printed Looping WHILE The EASI WHILE command provides a general purpose looping construct while log_expr statement list endwhile where log expr is a logical expression which is evaluated before each iteration of the loop statement list is the list of command statements to execute while the conditions for the loop hold true The statements in the body of the WHILE loop are executed as long as the logical expression in the WHILE statement evaluates to TRUE That is when execution reaches a WHILE statement the logical expression is evaluated andif TRUE the 66 PCI Geomatics Chapter 4 EASI Programming body of the loop is executed When execution reaches the ENDWHILE statement it jumps or loops back to when WHILE statement at which point the logical expression is evaluated again When the logical expression becomes FALSE execution transfers to the statement following the ENDWHILE otherwise the looping continues For example consider the following program local double NumberA input Enter a number between 1 and 25 NumberA while CNumberA lt O or NumberA gt 25 print T
147. s your day PRINTF File s is d x d with d channels n file dbsz 1 dbsz 2 dbnc File irvine pix is 512 x 512 with 11 channels A newline specifier n must be given in the format in order to force the cursor onto a new line This is different than the PRINT statement where a dollar sign must be appended to the PRINT statement to suppress the default new line REM REM is an internal remark comment statement which is ignored during execution The exclamation mark is a an acceptable synonym for REM 178 PCI Geomatics Chapter 8 EASI Language Reference REM text text any line of text RESET The RESET command forces EASI to reload system values from the parameter file RETURN The RETURN command returns execution control to the calling procedure and may optionally take an argument containing an expression whose value is to be returned to the caller Note that only user defined functions can effectively return a value RETURN expression Example define function pauaet x return x x enddefine RUN The RUN command runs a saved procedure file or PACE task R UN proc text ONERROR statement proc a procedure name or PACE task text optional message to pass to procedure statement error condition handler EASI User s Guide 179 Commands SEE The SEE command shows the current value of the parameter DEFINE is used to optionally print the min
148. se shapes endonerror 132 PCI Geomatics Chapter 7 Object Oriented Programming With EASI Dynamic Fields EASI classes provide a way to access pieces of data as if they are fields belonging to the object even if they aren t actual fields This method of access can be used to access dynamic data without having to build it directly into the objects corresponding class definition which should normally remain static Access to dynamic fields is obtained through two special methods which may optionally be defined for any class GetDynamicField and SetDynamicField The GetDynamicField method must be defined with a single argument expected to be a string If the method has been defined for a class when a field reference is performed for any object of the class and that field does not exist in the class definition then the GetDynamicField method is automatically executed The name of the field which could not be found will be passed to the function as its only argument The function would use this argument to determine an appropriate value and return that value using the RETURN statement The SetDynamicField method must be defined with two arguments The first argument will be a string containing a field name that was accessed but could not be found as part of an object on the left hand side of an assignment statement The second argument contains the value which was being assigned to the field The SetDynamicField
149. sizex x size of a pixel in georeferenced units sizey y size of a pixel in georeferenced units Note that x y geox and geoy change value for each pixel processed while dbx dby meterx metery sizex and sizey remain constant over the whole image It is usually necessary to use the x and y special variables when constructing subscript expressions for channel expressions For example the following assignment would mirror an image across a vertical centre line The dbx is used in computing the centre line 2 1 dbx x 1 y EASI User s Guide 193 Functions Functions The following subtopics are classes of intrinsic functions EASI functions supply capabilities which make developing procedures simpler and allow EASI to be used for calculator operations See Also DEFINE FUNCTION Calculator EASI has a number of intrinsic mathematical functions They return a numeric value and operate in double precision Function Type Description Argument Result SIN N Isine radians COS N cosine radians TAN N tangent radians ASIN N inverse sine note I radians ACOS N inverse cosine note 1 radians ATAN N inverse tangent note I radians LN N natural logarithm note 2 LOGIO N Ibase 10 Togarithm note 2 F EXP N natural exponent EXP10 N Ibase 10 exponent RAD N convert degrees to radians degrees radians DEG N convert radians to degrees r
150. sk is not runable 204 PCI Geomatics System Parameter Definitions This appendix contains procedures used to define system parameters and error messages for EASI EASI System Parameters 10 DOC Procedure DEFSYS EASI System Parameter Definitions 20 DOC 30 DOC This procedure defines the required system parameters for 40 DOC EASI PACE For GLE NEWENE Ya ENERE parameters should e 50 DOC defined at the beginning of the parameter file by running 60 DOC this procedure first when creating a new parameter file 70 DOC 80 local min max out 90 min 10000000000000000000000000 100 max 10000000000000000000000000 110 out 20000000000000000000000000 120 rem 130 DEF MODE C RUN Application Mode RUN MENU STAT 140 DEF SYSLABEL C EASI PACE System Site Label EASI User s Guide 205 Appendix B 150 DEF TERMINAL C VT100 Terminal Type See EASI Guide 160 DEF BELL C OFF Terminal Bell ON OFF 170 DEF MISSING M MISSING Missing Keyword for Status Reports 180 DEF REPORT C TERM Report Mode TERM OFF filename 190 DEF MONITOR C ON Program Progress Monitor ON OFF 200 DEF SYSERRORE N min max 0 EASI System Error Parameter 210 DEF E_PROMPT C EASI gt EASI Prompt String 215 DEF XPACERC N 0 max 1 Xpace Configuration 220 rem 230 rem The following parameters are required by EX1 amp EX2 programs 240 rem 250 DEF EX1 M EASI Example Pro
151. some experience working with EASI A Simple Procedure Suppose for example a hypothetical user often executes a sequence of tasks to resize and enhance an image Typically this user creates a new database using the CIM task copies data to it using the ll task computes a look up table for enhancement using the FUN task and then applies the look up table to the image using the LUT task Normally the user sets the parameters for the first task manually then executes it then sets the parameters for the second task and executes it and so on for each task in the list Such a 1 CIM III FUN and LUT are tasks that perform opera tions on database files and are not part of EASI itself EASI User s Guide 21 A Simple Procedure sequence of steps is an excellent candidate for automation using a simple EASI script An example of such a script is presented below The script is created by entering the commands that form the script in a text editor The script is then saved to a file with a maximum 8 character name all which must be upper case and followed by the extension EAS In the example below the script is stored in the file ENHANCE EAS Once created the script can be executed by entering its name with the RUN command as follows EASI gt run enhance The body of the script contains exactly the commands the user would enter manually in order to accomplish the desired task Typically this consists o
152. ssions or special format expressions which are evaluated and displayed Each numeric expression is evaluated to give a single numeric value which is displayed in a field of eight characters The decimal place is floated to take maximum advantage of the field size If the resulting value is an integer the decimal place will be dropped 172 PCI Geomatics Chapter 8 EASI Language Reference String Expressions Format Expressions Cursor Position The width of the numeric field can be modified with the RFIELD n expression Each string expression 1s evaluated and displayed with no extra padding between it and the previous field The format expression allows you to print data anywhere on the terminal quickly and easily clear portions of the screen and highlight characters in a number of different ways The syntax of this expression is Ccolumn row command command where e column is the terminal column to start printing e row is the terminal row to start printing e command is a format subcommand CLREOS CLREOL BOLD BLINK REVERSE UNDER ALLOFF or RFIELD The cursor position column row is optional If it is present both column and row must be specified If it is not present the current cursor position is used Examples PRINT C10 5 move cursor to column 10 row 5 PRINT 1 1 BOLD home cursor switch bold attribute on PRINT CCLREOL clear from cursor to end of line
153. stant indicating how many at most values will be shown el to 16 for numeric parameters 1 to 64 for character parameters min iS a numeric constant indicating at least how many values will be shown 0 to 16 for numeric parameters O to 64 for character parameters When a request for the status of a procedure is made EASI scans the procedure for STATUS_SHOW statements and does a SHOW on each parameter specified Ending a Status Report STATUS_END The STATUS_END command forces EASI to stop searching a procedure for STATUS commands It has the form STATUS_END and should be placed after the last STATUS_SHOW command STATUS _END is optional since it is implied at the end of a procedure however status reports for long procedures can be made faster using this command since only a part of the procedure is searched for STATUS statements Note Any STATUS commands after a STATUS_END will not be found 30 PCI Geomatics Chapter 3 Developing Simple Scripts Example Using STATUS With ENHANCE EAS In order to make the ENHANCE script work with STATUS the following lines are added to near the beginning of the script STATUS_TITLE ENHANCE Image Resizing and Enhancement STATUS_SHOW INFILE 64 1 STATUS_SHOW DBIC 1 1 STATUS_SHOW OUTFILE 64 1 STATUS_END With this addition the current values of the input parameters to ENHANCE can be determined interactively by the user using the STATUS command EAS
154. t parameters set e Chapter 3 Developing Simple Scripts describes how simple scripts can be created to automate the types of tasks performed manually in Chapter 2 e Chapter 4 EASI Programming provides an in depth description of EASI as a scripting language including coverage of data types and control structures e Chapter 5 Working with Data touches upon some of the more important intrinsic functions available in EASI using examples to demonstrate their use e Chapter 6 Error Handling describes techniques which can be used to take appropriate action when errors occur so that more robust and reliable applications can be created e Chapter 7 Object Oriented Programming with EAST describes support for object oriented programming such as the ability to define classes and member functions PCI Geomatics Chapter 1 Introduction e Chapter 8 EASI Command Line Interface presents reference material on all of the commands and intrinsic functions available in EASI e Appendix A Error Messages lists all of the error messages generated by EASI in alphabetical order e Appendix B System Parameter Definitions contains procedures used to define system parameters and error messages for EASI Throughout the manual numerous examples are used These examples are set apart from the text of the manual by being printed in a separate type face Many of these examples are give
155. t return gt backup one level 2 redisplay help EASI User s Guide 159 Commands The return key takes the help facility back one subtopic level It may be used in succession to return to the EASI level The question mark prints the text for the current help topic again in other words run that by me one more time It does not change the current subtopic help level The following diagram illustrates some of the help topics and subtopics that are available within the help facility The topic specifies the program or procedure on which information is requested Most topics contain several nested subtopic levels program CIM procedure SHELL HELP SYSTEM HELP MORE e e l DETAILS this help EXAMPLE DETAILS PARAMETERS FILE TEX1 TEX2 DBSZ PXSZ DBNC Example HELP CIM See Also KEY IF The IF statement is used to conditionally execute statements IFC logical_expression THEN statement_list 160 PCI Geomatics Chapter 8 EASI Language Reference ELSEIF logical_expression THEN statement_list ELSE statement_list ENDIF logical_expr A logical expression as described in the Logical Expression topic statement_list A list of one or more statements Each logical_expression is evaluated in turn until one of them evaluates to be true When one is true the corresponding statement_list will be executed and control will continue beyon
156. tation in the same fashion as a data reference local Circle c call c Setcenter 3 0 5 0 Like regular functions methods can take any number of arguments define local variables and may return a value A EASI User s Guide 121 Class Declarations class can have any number of methods associated with it The definition of the Circle class can be completed with a method to set the circle s radius and automatically compute the circle s area DEFINE METHOD SetRadius new_radius ON Circle this Radius new_radius l this Area 3 1415927 this Radius this Radius ENDDEFINE The following interactive example demonstrates use of the class Circle EASI gt local Circle c EASI gt call c Setcenter 3 5 EASI gt print c Area 0 EASI gt call c SetRadius 2 EASI gt print c Area 12 5664 It is not possible to overload a function name providing different function definitions depending on the number or type of its arguments It is possible to achieve some of the same affect in a manual way by using functions with variable number of arguments and the f partyp intrinsic to extract type information from arguments Inheritance A class may inherit data fields and method definitions from another class using the INHERITS keyword in its class definition define class class_name argl arg2 inherits parent_class enddefine 122 PCI Geomatics Chapter 7 Object Oriented Programming With EASI The newly defin
157. teractive use Consider the function following EASI script defined in the file TEST EAS The line numbers are for reference only and are not part of the actual code 1 local int fd num_pixels 2 co x DBOpenC pci demo irvine pix r 4 num_pixels DBPixels fd 5 6 local int dataline num_pixels 7 call DBReadLineC fd 1 0 O num_pixels dataline 8 call DBCloseC fd 9 10 local i 11 min_val 12 max_val nt min_val maxval 148 PCI Geomatics Chapter 8 EASI Language Reference 13 14 for i 0 to num_pixels 1 15 if C dataline i lt min_val min_val dataline i 16 if dataline i gt max_val max_val dataline i 17 endfor 18 19 printf The minimum value is d n min_val 20 printf The maximum value is d n max_val The script is intended to load the first line of data from the first channel of the file irvine pix and then compute the minimum and maximum data values in the file When run however the following error occurs Pe aa aa ea type mismatch lt if C dataline i lt min_val min_val dataline i It may not be immediately obvious why this happens To find out more we ll use the DEBUG support in EASI After entering EASI the script is first loaded EASI gt load TEST EAS next a breakpoint is set at the offending line EASI gt debug break test 15 The script can now be run It stops at the breakpoint EASI gt run test Halted at breakpoint 1 fun
158. the buffer is not of the same type as the data on the file the data is automatically translated to the appropriate type DBReadLines takes 6 arguments in order a file descriptor channel number a pixel offset from the left side of the image at which to start reading a line offset from the top of the image at which to start reading the number of pixels to read and the data buffer For example the following command will read all of the first line of data of the first channel call DBReadLine fd 1 0 O NumPixels DataBuffer Once the data has been read the contents of the buffer can be examined and manipulated For example the following loop determines the maximum value in the line of data local float MaxValue local integer i MaxValue DataBuffer 1 for i 2 to NumPixels 88 PCI Geomatics Chapter 5 Working with Data if C DataBuffer i gt MaxValue then MaxValue DataBuffer i endif endfor printf The maximum value in the line is f n MaxValue The DBWriteLine intrinsic is used to write data back to the file For example to copy the contents of DataBuffer into the last line of channel 2 call DBWriteLine fd 2 0 NumLines 1 NumPixels DataBuffer In this case the third and fourth arguments to the function are the x and y offsets to the start of the last line of the channel Maintaining History Records The database interface includes the ability to access history records History
159. the form DEFINE CLASS new_class_name fieldil_type fieldi_name field2_type field2_name ENDDEFINE For example the following declaration creates a class called Circle DEFINE CLASS Circle double Centerx double Centery double Radius double Area ENDDEFINE Once the class has been declared objects of the class can be declared using the LOCAL and GLOBAL commands This has the general form local class_name obj_name For example local Circle c CenterX 5 centery 3 Radius 2 57 Area 12 ANNAN 118 PCI Geomatics Chapter 7 Object Oriented Programming With EASI Data Field Access Restrictions The class Circle described above is hardly any different than a structure with the same name However class definitions in EASI allow restrictions to be put on the data fields belonging to a class A data field may be either PUBLIC READONLY or PRIVATE These restrictions control if a data field belonging to aclass may be read or modified by arbitrary EASI functions PUBLIC is the default access level and requires no special syntax during declaration In the previous example all the data fields of the class Circle such as Radius and Area have PUBLIC access A data field of type public is unrestricted and may be read and modified by any outside function Note that a STRUCTURE definition can be thought of as a class definition where all the data fields have public access and in which there are no
160. the value 3 will be assigned to the argument variable a and the value 7 will be assigned to the argument variable b Of course the function call will result in the value 7 being printed In addition to using literal values in the call statement variables and expressions may also be used local integer x y xX 3 y 2 call PrintMax x y 2 The argument variables declared in the variable definition are very similar to local variables For example it is possible to assign values to argument variables within the body of the function In most situations modifying the argument variable within the body of the function has no effect on the invoking procedure For example when the arguments in the function call are variables of any of the basic types like integer or float then even if the argument variable inside the function is modified the original variable when the function was called is not modified For example consider the following function which simply adds one to its argument define function increment a a a 1 enddefine Once the function is loaded the following sequence of commands can be executed local integer x x 10 EASI User s Guide 75 User Defined Functions call increment x print x However the final value of the variable x will still be 10 not 11 Only the value of the argument x is passed to the function However in some situations changes
161. this last case the has been substituted with the empty string Regular expressions may include any number of wildcard characters If the characters or need to be used in the regular expression but not as wildcards but as themselves then they must be preceded by the escape character The basic logical expressions described above can be combined with the logical relations AND OR and NOT to form more complex logical tests The AND relation applies to two logical expressions and will evaluate to TRUE if both logical expressions are themselves TRUE if C file irvine pix AND channel 1 print success The OR relation applies to two logical expressions and will evaluate to TRUE if one or both of the expressions is TRUE if C file irvine pix OR file demo pix print success The NOT relation applies to a single logical expression and will evaluate to the opposite or logical complement of the EASI User s Guide 65 Procedure Control expression That is the NOT relation applied to an expression will evaluate to TRUE of the expression is FALSE and will evaluate to FALSE if the expression is TRUE if C NOT file irvine pix print success Since the use of a logical relation is itself a logical expression logical relations can be combined to form more complex tests When combining logical relations it is often best to use bracket
162. tion The Initialize method is typically used for pre setting data fields within the object to particular values For example the initialize method could be defined on the Circle class presented above to initialize a circle object to unit size define method Initialize on Circle this SetRadius 1 0 enddefine Now whenever a circle is created it will automatically have its radius pre set to 1 EASI gt local Circle c EASI gt print c Radius 1 0 If an objects initialization requires arguments to specify values for the initialization this can only be accomplished by defining a separate initialization method with a different name and calling it explicitly for each object If an object has a parent class the Initialize method of the parent class will also be executed prior to the objects own Initialize method Similarly the Destroy method must also be defined without any arguments If it has been defined it will be executed automatically when an object is deallocated The Destroy method is typically used for freeing memory that was dynamically allocated by the object using the EAlloc intrinsic for closing files that the object may have opened and for other such clean up type activities For objects that are allocated using a LOCAL declaration its Destroy method will EASI User s Guide 125 A Sample Class be executed when the function in which it was declared terminates For objects that are allocated
163. to perform a keyword search of all the help topics online with a provided keyword predicate The first 100 help topics that match the keyword predicate are displayed and any one can be selected at the Enter topic name or lt RETURN gt for more prompt Once a topic has been selected from the matching list the user is placed in the normal help browser KEY keyword AND OR keyword 162 PCI Geomatics Chapter 8 EASI Language Reference The keyword predicate is a series of keywords each with an optional logical operation For instance vector OR image would list all topics with the vector or the image keywords while vector AND image would list all topics with both vector and image keywords The only possible operations are AND and OR but the default operation is OR if none is provided Thus vector line polygon is the same as vector OR line OR polygon Keyword searches are case insensitive and will match any subset of the keyword stored for a topic Therefore vector would find a topic with vectors or eigenvector Example KEY rasterize KEY vector AND export See Also HELP KEYWORDS LET The LET command assigns the value of an expression to a variable LET lvalue expression ONERROR statement lvalue parameter subscripted parameter or EASI variable expression A numeric
164. tring a line 2 EASI gt b 1 mstring b line 1 EASI gt b 2 mstring b line 2 EASI gt c a b EASI gt print c mstring a line mstring a line mstring b line mstring b line NENE Mixed String MString Expressions Mstring expressions are formed using string and mstring elements along with the concatenation operator Mstring expressions differ from string expressions in that they contain at least one mstring variable The result of an mstring expression is an mstring 58 PCI Geomatics Chapter 4 EASI Programming If an expression has the form MSTRING STRING the result is a new mstring formed by appending the given string as a new line at the end of the given MSTRING EASI gt local string s EASI gt local mstring ms result EASI gt s apples EASI gt ms 1 bananas EASI gt ms 2 pears EASI gt result ms s EASI gt print result bananas pears apples If the expression is of the form STRING MSTRING the result is an mstring formed by prepending a new line containing the given string to the beginning of the given mstring EASI gt result s ms EASI gt print result apples bananas pears If an expression contains a series of concatenations they are evaluated from left to right as either string concatenations or mstring concatenations or mixed string mstring concatenations depending on the types of data involved at that point in the evaluation This may prod
165. ts value while Transverse Mercator and Lambert Conformal Conic are examples of projections where additional values are required See Also Projections DBReadGeoInfo VECReadGeolInfo Reproject LOG The LOG command is used to control the user session log file When logging is active a record of various events is made in the log file such as the assignment of parameters and the launching of PACE programs LOG START LOG START filename LOG START level_number The LOG START command is used to activate session logging The default filename is EASI LOG which would be created in the local directory If another filename is supplied in the LOG START command it will override the default name If the log file already exists when logging is initiated additional log entries will be appended to the end of the log file If LOG START is given a numeric level number as an argument the Level of Interest can be modified The default level is four e Level 1 Record only user commands e Level 2 Record only messages from the LOG command e Level 3 Record LOG command messages and all PACE program executions e Level 4 the default Record LOG command messages PACE program executions and assignments to parameters EASI User s Guide 167 Commands LOG STOP The LOG STOP command is used to terminate logging LOG LIST The LOG LIST command will dump the contents of the currently active log or EASI LOG if
166. u should only exit using the BYE or EXIT commands This allows EASI to clean up before it exits If you exit any other way you may lose or harm files or lock devices EASI functions as an interactive command environment for executing tasks Input values required by tasks are specified through setting parameters which come in two main types string and numeric Within EASI parameter values can be 18 PCI Geomatics Chapter 2 Using EASI viewed using the PRINT and SEE commands and parameters may be assigned new values using the LET command Tasks generally declare a set of parameters which they use as input To view the parameters used by a particular task the STATUS command followed by the task name is used After setting a tasks input parameters the RUN command is used to execute the task Logging is available through the LOG command Log files can be created to save the contents of an EASI session to a text file Extensive on line help is available in EASI with the HELP command EASI User s Guide 19 Summary 20 PCI Geomatics Developing Simple Scripts An EASI script or procedure is a list of EASI commands stored in a text file Procedures can be as complex as an entire production research facility or as simple as a few interactive steps With procedures you can tailor the EASI system to your unique requirements This section assumes that you have read Chapter 2 Using EAST and now have
167. uce unexpected results if care is not taken for example EASI gt result mS S 5 EASI gt print result bananas pears apples apples but EASI gt result Ss S ms EASI gt print result applesapples bananas pears EASI User s Guide 59 Procedure Control This is because the EASI first evaluates s s as a string concatenation producing the result applesapples then the next concatenation operation results in the string applesapples being prepended to the given mstring The use of brackets is useful to ensure that concatention occurs in the way intended For example brackets around the previous example give a different result EASI gt result s S ms EASI gt print result apples apples bananas pears Procedure Control Procedure control is the ability to alter the flow of execution of a procedure It allows you to execute only certain sections of a procedure and to handle errors and special conditions Conditional Statements IF THEN ELSEIF ELSE ENDIF EASI allows the conditional execution of statements with the IF statement The IF statement can have various forms The simplest is a single test which if successful will cause a single statement to be executed if Ccondition then statement endif The condition to be tested may be any valid logical expression For example if a 3 then print success endif 60 PCI Geomatics Chapter 4 EASI
168. uent commands after it has been opened The second parameter r in the call to DBOpen indicates the file is to be opened with read only access Specifying r will open the file with read write access Reading General File Information It is often useful to obtain some information about the file like the number of channels it contains and their dimensions This information can be obtained once the file has been opened using the DBPixels DBLines and DBChannels intrinsics local int NumberOfChannels PixelSize LineSize PixelSize DBPixels fd LineSize DBLines fd NumberofChannels DBChannels fd if C NumberofChannels lt 1 then printf The file s contains no image data n FileName EASI User s Guide 87 Database Files return endif The type of a data channel can be determined using the DBChanType intrinsic function This intrinsic returns one of the strings 8U 16U 16S or 32R representing the four possible data types supported printf The first channel in the file is of type s n DBChanTypeC fd 1 Reading and Writing Image Data A line of data can be read into memory using the DBReadLines intrinsic First a data buffer needs to be allocated to hold the data being read from the file local float databuffer LinesSize DBReadLines can be used to read any part of a line from anywhere within the image directly into the data buffer If
169. uivalent to the following structure definition Table 3 Predefined Structures and Descriptions Vertex single 3 dimensional point Geolnfo projection information DEFINE STRUCTURE Vertex DOUBLE x DOUBLE y DOUBLE z ENDDEFINE The GeoInfo structure is more complex and its use will be discussed in a later chapter Pointers and Dynamic Allocation EASI provides functions that allow the user to directly allocate and manage blocks of memory and make it possible to build data structures such as trees and linked lists In some situations however considerable opportunities for misuse are available making it possible to not only cause errors but also to possibly EASI User s Guide 49 EASI Variables terminate EASI itself These powerful facilities should be used with care Pointers are special variables used to refer to allocated blocks of memory Pointers also have types indicating to EASI how a block of memory should be interpreted It is possible to declare pointers for any of the basic types in EASI as well as for structures The keyword PTR is used in LOCAL and GLOBAL declaration statements to indicate that a variable is a ptr For example the following statement will declare a pointer to a block of integers called pData local integer ptr pData When a pointer variable is declared it does not point to any block of memory the pointer is said to be initialized to NULL NULL is a keyword in E
170. ulating external data files However EASI allows the definition of functions which are similar to scripts but which may be called with a list of arguments and which are able to return a specified value The definition of a function is done within an EASI script In other words functions are defined in text files with the same naming conventions as EASI scripts Functions are not normally defined interactively at the command line An example of an EASI function definition is file USERFUNC EAS function to compute the average of two values DEFINE FUNCTION Average x y return x y 2 ENDDEFINE The statements within the body of the function are executed when the function is called EASI gt print Average 4 6 5 Note that a function should not have the same name as the script in which it is defined for example a function named test should not be defined in a file called TEST EAS Details on defining and using functions will be presented in a later section There are a number of special built in functions available in EASI which are known as intrinsic functions These special functions provide a number of important capabilities such as common numeric computations and file access An example of a simple numeric function is COS which returns the cosine of an angle in radians 40 PCI Geomatics Chapter 4 EASI Programming EASI gt print cos 0 5 0 877583 Many useful intrinsic functions w
171. uld be Procedure U Procedure V Procedure W GLOBAL STRING C c From V PRINT W C W i C From U RUN W RETURN RUN V RETURN C Back to U PRINT C The output from running U would be C From V Back to U Variable Declaration Local and global variables are declared using the LOCAL and GLOBAL statements respectively 54 PCI Geomatics Chapter 4 EASI Programming The LOCAL statement is used to declare one or more local variables of a particular type This statement has the basic form LOCAL type name name name where type is the type of local EASI variable to declare name is the name of a local EASI variable to declare Examples LOCAL INTEGER first second third LOCAL DOUBLE distance speed i LOCAL STRING winner teamname mvp If no type declaration follows a LOCAL statement EASI assumes the declaration type to be double however it is generally considered sloppy programming practice to declare a variable without explicitly specifying its type The GLOBAL statement has the same syntax as the LOCAL statement GLOBAL type name name name where type is the type of global EASI variable to declare name is the name of a global EASI variable to declare The GLOBAL and LOCAL declaration statements may be used any number of times at any place within a procedure The variable that is declared becomes available to the procedure immediately after the declaratio
172. ust have a defined value before it can be used in an expression Numeric expressions are evaluated using real arithmetic Examples 1 2 3 yields 6 2 1 3 3 yields 8 6 2A 5 yields 1 41421 i e square root SIN 3 1415927 2 yields 1 String Expressions String expressions are formed using string elements and the concatenation operator Concatenation is the act of placing strings together The result of a string expression is a single string A string element can be any of the following e astring constant e asubscripted string parameter e astring parameter e astring function e an EASI string variable e acharacter variable character array or subscripted character array e asubscripted mstring variable The single string operator is concatenation or string joining written EASI User s Guide 57 Expressions Example EASI gt print AB B13 ABB13 The double quote character may be included within a string by preceding it with a back slash character EASI gt local string message EASI gt message Finished processing file irvine pix EASI gt print message Finished processing file irvine pix MString Expressions Mstring expressions are formed using mstring elements along with the concatenation operator The result of an mstring expression is an mstring EASI gt local mstring a b C EASI gt a 1 mstring a line 1 EASI gt a 2 ms
173. ut the area of operation is still that indicated in the MODEL statement not necessarily that of the override database The following commands are an example of this The irvine pix file is 512x512 and eltoro pix is 1024x1024 The following operation copies channel 1 of eltoro pix to channel 8 of irvine pix but because irvine pix is the implicit database the area of operation is 0 0 512 512 and so only the top left quarter of eltoro pix is copied into channel 8 of eltoro pix MODEL ON irvine pix 8 pci demo eltoro pix 1 ENDMODEL 190 PCI Geomatics Chapter 8 EASI Language Reference The second part of the channel specification is the subscript specification which is optional In the above case we used the default subscript specification which x gt x y gt y The subscript specification allows us to indicate what pixel should be operated on for the current value of X and Y and may be given as an expression The following example is similar to the last but actually assigns a sampled copy of eltoro pix to irvine pix The x and y symbols are the current pixel location when the expression is evaluated for each pixel MODEL ON irvine pix 8 pci demo eltoro pix 1 C x 2 1 y 2 1 ENDMODEL In the above expression X and Y vary from 0 to 511 as the implicit window of operation is 0 0 512 512 the area of irvine pix However channel 1 of eltoro pix is sampled for values of 1 t
174. when the procedure is executed to ensure they are valid Defining New Parameter Entries DEFINE In addition to all the standard system and application parameters you can define new ones for your own personal applications for example work parameters for procedures or new parameters for tasks However unless these definitions are included in the system definitions by the system manager they will be local to your account only and will be lost if your parameter file is deleted You can save your new definitions in a procedure file to run whenever you create a new parameter file Parameter names are from one to eight characters long The first character must be a letter A Z The following zero to seven characters can be any combination of letters A Z EASI User s Guide 25 Defining New Parameter Entries DEFINE digits 0 9 underscore _ hatch or colon By convention hatches and colons are rarely used and even then only as the last character in a name There are three types of parameters Message String and Numeric Message parameters are used to hold messages of up to 64 characters Once defined they should not be changed The syntax for defining a message parameter is DEF parm M message descriptor where parm is the 1 to 8 character name of the message M indicates a message parameter message is a message of up to 64 characters descriptor is a descriptor of up to 32
175. wing the case value If no match is found execution will continue with the next statement after the CASE statement NOTE The CASE statement cannot be used in within raster models Example CASE command HELP help_cmd STOP stop_cmd See Also IF DEFINE The DEFINE command is used to define a number of different things It can be used to define new parameters in the PRM PRM file new data types and new functions The DEFINE command defines a new parameter in the parameter file DEF INE parm M text desc DEF INE parm al c def desc DEF INE parm N rmin rmax rdef desc parm up to 8 character parameter name M C N parameter type Message Character Numeric text up to 64 character text message 142 PCI Geomatics Chapter 8 EASI Language Reference desc optional 32 character prompt descriptor def zero to twelve character default string rmin minimum real value rmax maximum real value rdef default real value If the parameter already exists it will be assigned the new definition Note that this changes the value of the parameter back to the assigned default The PACPRM EAS procedure is normally used to build new PRM PRM files and consists of a group of procedures in the F PCIHOME pro directory such as DEFKERNE EAS These procedure contain a DEFINE statement for each parameter in the PRM PRM file Example DEFINE FILE C aa Database F
176. y also count by non integral values using an increment such as BY 0 5 Branching GOTO It is possible to transfer execution to any line within the same procedure by using the GOTO statement The form of the statement is GOTO location where location is an existing line number between 1 and 9999 or a statement label Example 1 goto 1500 Example 2 if VALUE gt 0 then goto 57 endif Example 3 SMALL print This amount is insignificant This next part comes later in the program if AMOUNT lt 5 then goto SMALL EASI User s Guide 69 Procedure Control endif The GOTO statement can redirect the path of your procedure in a host of new directions freeing you from programming in a strictly linear fashion You may have noticed that until now there has not been any discussion regarding the use of line numbers EASI can accept a program that uses line numbers to identify command lines but line numbers are not necessary Since EASI follows your instruction in a line by line fashion lines of procedure are executed in order This makes editing the structure of a procedure much less tedious However commands such as the GOTO command present special concerns since they clearly need some form of specific direction or address to complete their task Using labels along with the GOTO command solves this problem A label is not so much a command as it is a beacon Label formats are limited only to
177. y calling DBWriteHistory without specifying a message A special message Operation Aborted will be written to the file When the operation is completed successfully a new history message can be written and special logic will cause it to overwrite the Operation Aborted message instead of pushing it down When using this technique EASI code has the following form where the variables filename channel and message are assumed to have been defined fd DBOpen filename r call DBWriteHistory fd IMG channel do some processing on the channel cal 1 DBwWriteHistory fd IMG channel message call DBCloseC fd History records can be read using the DBReadHistory intrinsic For example to read the most recent history record for the look up table in the segment stored in the variable segnum into a string variable called description description DBReadHistory fd LUT segnum The second and third arguments to DBReadHIstory follow the same conventions as for DBWriteHistory An optional fourth argument to DBReadHistory specifies a specific history 90 PCI Geomatics Chapter 5 Working with Data record to read For example to read the third most recent history record description DBReadHistory fd LUT segnum Accessing Database Segments The database interface also includes functions to access database segments or layers Segments are parts of the

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