its on my site http://www.jpg2bmp.com

the major item its to collect the rgb color of one point in a grid of 4x4 or 8x8 or 16x16 or 32x32 and if the other colors dont match in 256 abs range puts the color elsewise just put the 768 colors or 12288 colors or 49512 colors it give less colors and a good approax to the original image ,the png file; after zpaq compression on a bmp fits in 29% of the original
theres also my bmx format for blurry jpgs

do take a look

I know its promoting a site but its major off topic!