GIMP Usage

Interface

• If you run the GIMP under KDE, start it in a new desktop: that's currently the only way I found to get all the GIMP windows to reappear when working with multiple applications.
• All tools have simple key shortcuts that are very useful, try to remember them.

Saving

• PNG format allows you to choose the compression level. The default maximal compression level acts strangely (artifacts on the image), so if that happens reduce the compression level to 5-6.

Selection

• When making a selection, for example with the rectangle tool, you have to confirm it by clicking on it. Until this click, the selection is easily modifiable by using the sub-rectangles appearing
• A selection also usually shows the layer boundaries (which is a good thing).
• You can create a new selection based on a layer "contents" (parts that are not transparent). This is done by right-clicking on the layer and choosing "Alpha to selection".
• If you create a anti-aliased selection, this will apply to future operations. For example, a fill on an anti aliased rectangle will not fill uniformly the rectangle with the color; the edges will get a smooth transition.

Scripting

• Scripting the GIMP can be done easily using the Python API. You can write pure Python scripts, and you don't need to use Scheme at all.

• In order to make your Python script accessible from within the GIMP, you need to save it in ~/.gimp-2.4/plug-ins/. You need to make it executable or GIMP won't recognize it.

• In your script, you need to have the register() function and a main() function which can be empty, in addition to your actual function which executes what you want. Here are the arguments for the register function (with an example):
  • "generate_rounded_corners": Name of the plugin (how to call it programmatically with Script-Fu)
  • "This is a test Python plugin." : Textual description
  • "It creates and saves an image.": Other description (extended, not sure here)
  • "Elvanör": Author
  • "Jean-Noël Rivasseau": Copyright owner
  • "2007": Date
  • "_Rounded Corners...": Name of the plugin (in the GIMP menus)
  • "RGB*, GRAY*": Modes accepted (??)
  • []: Arguments to this plugin
  • []: Return values of this plugin, only useful in non interactive mode
  • generateRoundedCorners: Python callback function (essential!)
  • menu="<Image>/Filters/Render/Rounder Corners": Path in the menus

• In the previous list, the arguments list has the following syntax:
  • PF_STRING: type of argument
  • "targetDirectory": argument name
  • "The directory in which will be saved the images": description
  • "/srv/": Default value. This is used *only* in the interface, eg. when using the plugin non interactively you must always pass the correct number of arguments.

• The _() function that you can see used in example plug-ins is for internationalization. The "_R" in "_Rounded Corners..." is for the mnemonic, eg the key that will be associated as a shortcut in the interface.