Dedicated to image composition, image authoring and photo retouching, this open source software presents itself as the main competitor for the famous (and expensive) Photoshop. GIMP (for GNU Image Manipulation Program) allows you to simply create images, retouch photos, and even batch convert or render images massively. This freeware is also modular : it can be upgraded with plug-ins and extensions to do almost anything. With its advanced scripting interface, you'll be able to easily script image-manipulation procedures. If you're a Photoshop user, you'll need to get used to The GIMP's approach which is slightly different.

The GIMP need the GTK+ Runtime Environment to be installed on your computer. For Windows NT/2000/XP.