The Gimp

Info

The GIMP "Gnu Image Manipulation Program" : One of the most powerful general-purpose image editors around, the upgrades make the GNU Image Manipulation Program eminently comparable to Photoshop.

Older features include channels, layers and masks, filters and effects, tabbed palettes, editable text tools, perspective clone, improved printing, and color operations such as levels. New improvements include GEGL integration for 32-bit color support, dynamic brushes, and more options for the free select tool.
It even has regex-based pattern matching for power users.

ScreenShot

gimp01
Licence: GPL
siteWebsite