GNU Image Manipulation Program (GIMP)
From The Glossary of Digital Photography
An image-manipulation program created as a student project in the mid 1990s by Spencer Kimball and Petter Mattis, two University of California at Berkeley students. GIMP became the first major application software program offered free to end users instead of programmers. It was originally designed for Linux operating systems, but now there are versions available for Windows and Mac OS X. Although freely available, it lacks features important to higher-level digital photographers, such as native support for adjustment layers, support for color management, 16-bit images, native support for CMYK, and a few other features. For someone just starting out, it can be a powerful as well as a free tool. See also XCF
