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.

>>100
Anything that doesnt achieves far worse compression ratio. Still they are faster than huffman codes and bit-shifting isnt an expensive operation.
You trolled me real good, you made me actually check.

I used a LZW compressor I found somewhere which performs about 10-30% better than the classical compress, which also performs better than a textbook LZW implementation.

On the other side of the ring we have LZO (the free, old and busted version) since it's what I had at hand.

The test corpus is a bunch of files (about 45% text, 25% executables, 15% uncompressed images, 15% random crap) totaling 300MB. LZMA compresses this to less than 90MB.

Compressor   Compressed size   Compression time   Decompression time
GZIP -6      110825245          14.86             9.79
LZOP -9      124417663          61.45             4.51
LZW          147157939         147.87             5.47
LZOP -1      148794061           3.55             3.26

The conclusion here is that only somebody clinically retarded would use LZW.

If you know of some supposedly better LZW implementation please do tell.