Notes on GIMP Scripting


C, Script-fu, Python: first-class citizens
Perl, C++, C#, Ruby: need to find and build a module; not well supported.



Help strings: first is short, second is long.

Names: first is script author, second is copyright owner.

Leave output parameters blank, []

Remember to call main() at the end of your Python script.

Image type examples:

Create a new image -- don't run from an existing one
Accept any type of image
RGB only, no alpha channel (no transparency)
Only RGB with transparency
RGB with or without transparency
Only grayscale, no transparency
Grayscale with or without transparency
Only indexed, no transparency
Accept RGB with transparency, Grayscale with or without, and Indexed only without transparency.
You get the idea -- combine them as needed! But most people will only need "" and "*".

Input parameters:

For a complete list, see the example code.

When writing a plug-in that operates on an image, the first two input parameters should be:

          (PF_IMAGE, "image", "Input image", None),
          (PF_DRAWABLE, "drawable", "Input layer", None),
and your function definition should take img and layer as its first two arguments.

For functions that create a new image, you don't need image and drawable.

Installing a Python script:

Use Preferences, Folders->Plug-ins to find location of plug-ins on your system. You'll see two: one is the system location (may be overwritten when you reinstall GIMP), one is your personal plug-ins folder.

On Linux it's ~/.gimp-2.6/plug-ins/

Don't forget to make it executable: chmod +x ~/.gimp-2.6/plug-ins/

Must restart GIMP when you add a script or change register(). No need to restart when changing other parts of the script -- it runs as a separate process and will be re-read from disk each time.

Custom dialogs:

Can use anything from pygtk.

See or for examples.

Direct pixel access:

Read pixels with tiles or pixel regions.

Write pixels with pixel regions.


  • (tiles and pixel regions)
  • (pixel regions only)


To see output of print, run from a terminal, or tail -f ~/.xsession-errors

Python debuggers work if you can attach to the process -- plug-ins run in their own process.

Python console:



>>> gimp.image_list()
[<gimp.Image 'img_1444.jpg'>,
 <gimp.Image 'sea-nettle2.jpg'>]
>>> img = gimp.image_list()[1]

>>> dir(img)
(lots of output)

>>> layer = img.active_layer

>>> layer.width

Python-Fu documentation:

Documentation on the basic GIMP Python objects, like gimp, pdb, Image, Layer, Drawable:

Look up PDB functions in GIMP's Procedure Browser, Help->Procedure Browser

Procedure Browser to Python:

  • Change dashes to underscores
  • Omit any run-mode parameter
  • Change -1 to None

Installing GIMP-Python on Windows

Do these in order:
  1. Install Python (
  2. Install pygobject, pycairo, and pygtk (
  3. Install GIMP (


Based on Tiny Scheme.

Use the Tiny-Fu Migration Guide (from scripts written for GIMP 2.2 and earlier) -- which also points to best practices in script-fu development.

Installing script-fu:

Install to ~/.gimp-2.6/scripts/ -- or whatever Preferences says for Folders->Scripts

Then: Filters->Script-Fu->Refresh Scripts

Must Refresh Scripts every time you change a script-fu.

Defining variables:

(let* ( (var1 val)
        (var2 val)

You can also use let (without the *) -- difference is that let* lets you refer to var1's value in var2 def, etc. When in doubt just use let*.

Lisp syntax:

car gives the first element of a list:

> (car '(one two three (a b c) four five))


cdr gives the rest of the list, e.g. (two three (a b c) four five)

(if (= (car (gimp-selection-is-empty img))
    (gimp-message "Nothing is selected")
Always use car: all script-fu functions return a list:
> (gimp-selection-is-empty img)

Group statements with begin:

(if (= (car (gimp-selection-is-empty img))
      (gimp-progress-update percent-done)
    )    ;; end "if selection empty"
    (gimp-message "Nothing is selected")  ;; !empty

Loops: use set! to update a variable you've already declared with let*:

    (while (<= y height)
           (set! y (+ y 1))

Common Tiny-Fu errors (watch out for these!):

  • Using set! rather than let or let*
  • Not checking for null before using a list
  • Using nil (use '() instead)
  • Fractional numbers must start with 0: 0.5, not .5 (this one might be fixed now)

    Script-Fu Debugging:

    (gimp-message (string-append "Width is: "
                                 (number->string width)))
    or, sadly, binary search: delete half the file and see if the error goes away.

    Script-fu console:

    > (gimp-image-list)
    (5 #( 9 8 7 3 1 ))
    > (define img2 (aref (cadr (gimp-image-list)) 1))
    > (define layer (car (gimp-image-get-active-layer img2)))
    > (gimp-drawable-width layer)
    > (gimp-image-width 3)

    Script-Fu Documentation:

    Look up PDB functions in GIMP's Procedure Browser, Help->Procedure Browser

    Kevin Cozens's wiki

    Finding sample scripts:

    GIMP source -- including the online git tree:




    Also GIMP Plug-in Registry

    or google gimp script or gimp plug-in