I've thought about writing a book on that.I've had to implement bits and pieces of PDF,PNG,JPG,and TTF and learning this stuff has been fascinating.

I did write one article and also did a short video on this stuff, but could think about expanding that if there is sufficient interest.

http://www.youtube.com/watch?v=BLnOD1qC-Vo http://practicingruby.com/articles/shared/oelhlibhtlkx

My work so far has been in Ruby but I'd probably want to at least look into how to do this sort of stuff in C or some other low level language, because things like alpha channel splitting in PNG is painfully slow :-/