Gimp

GIMP 2.4.4 is the most extensive and best free software for photo editing.

This free, originally developed for Linux, software is also available for Windows and Macintosh.

GIMP can compete with the familiar Photoshop on many functions. If you are not a professional graphic designer, you can easily can work with this program.

GIMP contains a lot of options for editing pictures. Of course, this free program can perform the following edits on pictures:
- increase/decrease
- rotate and cut
- color/contrast adjustment
- retouch
- erase, airbrush and pencil
- select on color, shape
- measure corners
- etc.

GIMP is a must have!