Free Professional Digital Photo Editor
The GIMP (The GNU Image Manipulation Program) is a professional digital
photo editor that is the open source answer to Adobe Photoshop. It has a
raster image editor that is the envy of commercial editors. The GIMP's
tools can do the unimaginable with any image you want to edit or build from
scratch. It can be used as a simple paint program, a photo retouching
program, an image renderer, or an image format converter. The GIMP supports
layered design, gradients and an endless list of incredible functions.