Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!gem.mps.ohio-state.edu!apple!motcsd!hpda!hpcuhc!hpspcoi!jchristy From: jchristy@hpspcoi.HP.COM (Jim Christy) Newsgroups: comp.graphics Subject: Re: color dithering? Message-ID: <1360001@hpspcoi.HP.COM> Date: 2 Oct 89 04:38:18 GMT References: <6350007@hpcupt1.HP.COM> Organization: HP PCG, Sunnyvale CA Lines: 20 Color dithering is a simple extension of mono dithering. You simply dither each color component separately before combining them to create your final pixel value (index into your color lookup table [LUT]). In other words, treat each color channel as you would a gray-scale. Then dither using any favorite dithering technique. Foley and Van Dam discuss this in some detail in Fundamentals of Interactive Computer Graphics. It helps if you divide your color LUT uniformly among all three primaries. Then your pixel value (LUT index) encodes what color you will actually get. In your case, divide your 6-bit pixels into 2 bits of red, 2 bits of green, and 2 bits of blue. Now program your color LUT based on this ordering. After dithering each color component, you get a value between 0 and 3 for each of red, green and blue. Now form your final pixel value by shifting these numbers the appropriate number of places and ORing them together. jhc