I recently stumbled across this whilst sifting through the Weird Wild Web:
The Definitive Guide
Released under the GNU Free Documentation License, V1.1.
If you deal with image processing software then you really need to know about PNG. Superior to JPEG for images containing sharp edges and step gradients (i.e. line art and such), PNG uses a non-patented lossless data compression method. While it won’t compress down as much as JEPG, it also doesn’t suffer from high-frequency signal loss, generation loss and compression artifacts (checkerboarding and such). Also see the Wikipedia article on PNG: