Perl Graphics Programming

Your First Gimp Script

When a plug-in is selected from one of the Gimp’s menus, it looks at the Procedural Database to determine which function should be called. For a plug-in written in Perl, this means that it calls whatever subroutine you have registered. The Gimp collects parameter data from the user via a dialog box (see also the Standalone Scripts section at the end of this chapter), and then passes it off to the Perl script.

Every script written using Gimp::Fu starts with a call to the register method, which adds the script to the PDB. The register method performs the following functions:

• Defines the plug-in documentation

• Defines the plug-in’s place in the menu hierarchy

• Defines the types of images accepted by the plug-in

• Defines the arguments expected by the plug-in

• Defines the values returned by the plug-in

• Installs the plug-in in the Procedural Database

• Performs additional error checking and feature checking

See Appendix B for a reference table that covers all of the parameters and types expected by register.

The introductory script in Example 5-1 illustrates the use of the text tool and the proper way of handling font information. The example takes a string and breaks it up into a grid of characters, as shown in Figure 5-1.

Figure 5-1. A grid of letters created with the text tool

First we import the Gimp and Gimp::Fu modules. The Gimp uses a program called gettext to handle the translation ...