I needed to directly modify pixel values of several images in a special way. First, I looked into Gimp’s Script-Fu functionality, but this seemed too complicated for what I needed so I decided to write such one-off utility in Java.
It simply reads all GIF images in specified directory, does some custom transformation of pixels, and then writes images back onto disk. It is really quick’n’dirty so be warned
Source code: ImageManipulation.java