ITT Rule IDL Version 7.0 User Manual download pdf (Page 273)

Chapter 10: Creating a File Writer 273

iTool Developer’s Guide Example: TIFF File Writer

IF (self->IDLitWriter::Init('tiff', $

TYPES=['IDLIMAGE', 'IDLIMAGEPIXELS', 'IDLARRAY2D'], $

NAME="Tag Image File Format", $

DESCRIPTION="Tag Image File Format (TIFF)", $

_EXTRA = _extra) EQ 0) THEN $

RETURN, 0

RETURN, 1

END

Discussion

The first item in our class definition file is the Init method. The Init method’s

function signature is defined first, using the class name example1_writetiff. Note the

use of the _REF_EXTRA keyword inheritance mechanism; this allows any keywords

specified in a call to the Init method to be passed through to routines that are called

within the Init method even if we do not know the names of those keywords in

advance.

Next, we call the Init method of the superclass. In this case, we are creating a subclass

of the IDLitWriter class; this provides us with all of the standard iTool file writer

functionality automatically. Any “extra” keywords specified in the call to our Init

method are passed to the IDLitWriter::Init method via the keyword inheritance

mechanism.

We specify a list of accepted filename extensions (

tiff, in this case) via the

Extensions argument, and set the TYPES keyword equal to the iTool data type of data

that can be written using this file writer. (The iTool data types specified by the

TYPES keyword must match the iTool data type of the data selected in the iTool

Export Wizard in order for the file writer to be available for selection.)

We specify a value for the NAME property of the writer object (this is displayed in

the system preferences dialog) and include a description of the writer via the

DESCRIPTION keyword. Finally, we use the _EXTRA keyword inheritance

mechanism to pass through any keywords provided when the Init method is called.

Finally, we return the value 1 to indicate successful initialization.

SetData Method

FUNCTION example1_writetiff::SetData, oImageData

; We need a filename for the file we are about to write.

strFilename = self->GetFilename()

IF (strFilename EQ '') THEN $

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ITT Rule IDL Version 7.0 User Manual Page 273