10.7. The “Script-Fu” Submenu

10.7. The “Script-Fu” Submenu
	10. The “Filters” Menu

This submenu contains some Script-Fu commands, especially the Script-Fu console. Script-Fu is a language for writing scripts, which allow you to run a series of GIMP commands automatically.

10.7.1. Activating the Submenu

You can access this command from the main menu through Filters → Development → Script-Fu.

10.7.2. Script-Fu Console

The Script-Fu console is a dialog window where you can interactively test Scheme commands.

The console consists of a large scrollable main window for output and a text box at the bottom to enter Scheme commands. When you type a Scheme statement and then press the Enter key, the command and its return value will be displayed in the main window.

Figure 16.234. The Script-Fu Console

You will find more information about Scheme and examples how to use the Script-Fu console in Section 3, “A Script-Fu Tutorial”.

The Script-Fu Console Buttons

Browse

The Browse button is next to the Scheme commands text box. When clicked, the procedure browser window opens with an additional Apply button.

Select a PDB procedure from the list and press the Apply button. The selected procedure and its parameter names will be pasted into the text box of the Script Console.

Now you just have to replace the parameter names after the procedure name with actual values. Then you can call the procedure by pressing Enter.

Close

Pressing this button closes the Script-Fu console.

Clear

When you click on this button, the content of the main window will be removed. Note that you can't get back the removed content using the Save command.

Save

This command lets you save the content of the main window, that is the Script-Fu console output (including the “>”-characters).

10.7.3. Start Server

This command will start a server, which reads and executes Script-Fu (Scheme) statements you send it via a specified port.

Figure 16.235. The Script-Fu Server Options

Listen on IP: The IP address the Script-Fu server will listen on. This is usually 127.0.0.1 (also known as localhost). Only change this if you know what you are doing.
Server Port: The port number where the Script-Fu server will listen. It is possible to start more than one server, specifying different port numbers, of course.
Server Logfile: Optionally you can specify the name of a file the server will use to log informational and error messages. If no file is specified, messages will be written to stdout.

The Script-Fu Server Protocol

The protocol used to communicate with the Script-Fu server is very simple:

Every message (Script-Fu statement) of length L sent to the server has to be preceded with the following 3 bytes:

Table 16.1. Header format for commands

Byte #	Content	Description
0	0x47	Magic byte ('G')
1	L div 256	High byte of `L`
2	L mod 256	Low byte of `L`

Every response from the server (return value or error message) of length L will be preceded with the following 4 bytes:

Table 16.2. Header format for responses

Byte #	Content	Description
0	0x47	Magic byte ('G')
1	error code	0 on success, 1 on error
2	L div 256	High byte of `L`
3	L mod 256	Low byte of `L`

	Tip
	If you don't want to get your hands dirty: there is a Python script named servertest.py shipped with the GIMP source code, which you can use as a simple command line shell for the Script-Fu server.