ImageMagick

ImageMagick is an image manipulation software suite compatible with more than 100 image formats. It is a GPL compatible Open Source software that may be freely used, copied, modified, and distributed.

Use it for Format Conversion, Transformation, Special Effects, GIF animation sequence and many more operations.

Look at a list of tools that use ImageMagick, including a FAQ on ImageMagick Usage.

Other related resources:

• Open Source Images
• Moving to Freedom: free software, free culture, free association
• Innovations in Digital Asset Management, Circa 2008