Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!think.com!spool.mu.edu!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!liuida!isy!lysator.liu.se!zap From: zap@lysator.liu.se (Zap Andersson) Newsgroups: comp.graphics Subject: Re: Color quantization ideas: To histogram or not to histogram, comments? Keywords: graphics quantization Message-ID: <609@lysator.liu.se> Date: 3 May 91 05:50:02 GMT Article-I.D.: lysator.609 References: <606@lysator.liu.se> <3931@ssc-bee.ssc-vax.UUCP> Sender: news@isy.liu.se (Lord of the News) Distribution: comp Organization: Lysator Computer Club, Linkoping University, Sweden Lines: 57 coy@ssc-vax (Stephen B Coy) writes: >>However, the RESULT of my renderer is MUCH better 8 bit images than using >>any 'standard' algorithm. >Rendering and color quantization are two seperate processes. Are >you saying that your renderer is better than others you've seen or >that your quantization is better? Ok, I've tried Autodesk 3D studio. Output stinks in 320x200 VGA. I've tried Autodesk renderman and quantized with their own 'convert' program. Still stinks (same algo I assume). I think they prequantize to 5 bits, then do some median-cut with or without dithering (dont know what kind, guess it's floyd-Steinberg). I still think it stinks. Perhaps, like you said , it's all in the 5 bit preQ that i do not do. Dont know. (My 'aim' with my posting was to get some interesting discussion back into comp.gfx) :-) >>15 bits (32768 colors). BUT 5 BITS PER COLOR IS NOT ENOUGH! >You're right. For most images 5 bits is not enough. I've found for >converting to VGA that 6 bits works best. Since VGA cards have >6-bit DACs this should be no surprise. Keeping track of 18bit color >running under MSDOS is challenging but not impossible. Ah, but could someone tell me WHY i should keep track at them ,eh? Here is the hated histogram again! I can agree that you have a one- bit histogram that tells if a color is used at all or not. But not more. >BTW I've seen some of the anims from RayTracker. Looks like a nice >program. If you'd like to see what I consider fairly good Ehem :-) some of the tolsun.oulu anims are farily old (sweat shudder) so you shouldn't (sweat shudder shudder) judge on those (sweat sweat) :-) I could mail you a new-ish image if you like. Just mail me a 'yo'. >quantization get a copy of my ray tracer, Vivid. It's somewhere out >there... The quantization program I include does do a histogram but >allows you to limit the max count for a color. Sounds clever! >Stephen Coy >coy@ssc-vax.UUCP -- * * * * * * * * * * * * * * * * * (This rent for space) * My signature is smaller than * Be warned! The letter 'Z' is Copyright 1991 * yours! - zap@lysator.liu.se * by Zap Inc. So are the colors Red, Green and * * * * * * * * * * * * * * * * * Greenish-yellow (Blue was taken by IBM) -- * * * * * * * * * * * * * * * * * (This rent for space) * My signature is smaller than * Be warned! The letter 'Z' is Copyright 1991 * yours! - zap@lysator.liu.se * by Zap Inc. So are the colors Red, Green and * * * * * * * * * * * * * * * * * Greenish-yellow (Blue was taken by IBM)