It strips the blue channel, offsets the red and green channels, and then changes it to a bmp format, then saves the resulting file with the bum extension. I don't think it's an algorithm so much as it's more or less a script.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)