Are there any open source sprite format?

PNG just plainly sucks. I has no support for animations, timing or delta compression and sequence names. Also, PNG is slow at random access (you have to decompress image before use). Proprietary formats (like Diablo 2 DCC) are much better, but highly specialized for their games: some have no true color, other have no directions.

>>99
asically you have a bitmask every once in a while telling you which bytes are literals and which ones are matches.
I've seen it used in Stonekeep sprites. Had to disassemble .exe to get algorithm.