Unrelated, but if anyone want to convert color graphics to grey:
R 0.299
G 0.587
B 0.114
R+G+B = 1.0
I found this out when I wrote a Floyd-Steinberg dithering routine. Without evaluating the error of the color selection properly, the dithered image would become slightly green toned.
Another issue was that a 50% b/w pattern would become 70.7% grey (1/sqrt(2)), not 50% grey. So I had to correct that too. AFAIK, I'm the only one that have adressed that issue (that statement includes Photoshop, GIMP and NetPBM).
