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.

>>44

this could also be due to system opengl drivers, your video card drivers, etc. also, color values represented as 0 to 255 integers are going to be turned into a 0 to 1 number in opengl, and depending on your gfx card, some precision might be lost.