230 Chapter 9: Creating a File Reader
Overview of iTool File Readers iTool Developer’s Guide
Overview of iTool File Readers
A file reader is an iTool component object class that defines how data stored in a file
should be imported into the iTool environment. File readers have mechanisms for
determining the type of data stored in a file, which allows them to create IDLitData
objects from the stored data. Some file readers implement a graphical user interface
allowing the user to specify the format of data before importing into the iTool; others
read a well-defined file type and operate more or less automatically. Some examples
of iTool file readers are:
• the ASCII file reader, which uses the IDL ASCII_TEMPLATE and
READ_ASCII functions to allow the user to define the format of data in a text
file,
• various image file readers, which allow the user to import data stored in JPEG,
BMP, PNG, and other well-defined image format files,
• a generic binary file reader, which allows the user to specify the format of files
containing binary data.
A number of standard file readers are predefined and included in the IDL iTools
package as described in “Predefined iTool File Readers” on page 231.
The File Reader Creation Process
To create a new iTool file reader, you will do the following:
• Choose an iTool file reader class on which your new operation will be based.
In almost all cases, you will base your new operation on the IDLitReader class,
which handles registration of standard file properties and provides standard
messaging features.
• Provide methods to check the type of data stored in the file and place the
retrieved data in a data object.
• Set data object properties.
This chapter describes the process of creating a new file reader based on the
IDLitReader class.
