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.

>>69
That explains why it sucks and uses primitive LZ77 (developed by two stupid jews), instead of much cooler LZW.
"LZ" refers to Abraham Lempel and Jacob Ziv in LZ77 as well as in LZW. If these are your two "stupid jews", you might want to reconsider your argument.

Now, the compression part itself of PNG isn't particularly brilliant all things considered (specially for natural true-color images), but you'll be hard pressed to find sets of data where "LZ77" (in fact it's DEFLATE, which you could say is LZ77 backed by Huffman) performs worse than LZW.

I am very well aware IHBT.