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From: massa@uni-paderborn.de (Michael Janich)
Newsgroups: comp.sys.amiga.programmer
Subject: xxx to HAM algorithm
Summary: A algorithm to convert a grafik file with more than 32 colors to HAM
Message-ID: <1991Jan23.170826.6194@uni-paderborn.de>
Date: 23 Jan 91 17:08:26 GMT
Organization: Uni-GH Paderborn
Lines: 32

Hi out there,

I'm searching for a GOOD algorithm to convert more than 32 colors to HAM. I
saw the following:

(ppmtoilbm)
	-Color map are the 16 gray scales (000, 111, ...)
	-calculate for the 4 possibilities (change red, blue, green or take
	 color map) the differences like
		delta_green = abs(oldred - red) + abs(oldblue-blue);
	-take the minimum of these differences.

The output is ugly - compared with that from HamLab (in my opinion the best
GIF2HAM converter).

So I tried 
	-Color map are the 16 most used colors
	-<rest the same>
But now I have green areas in the picture.

Can anybody please help me - perhaps with the HamLab algorithm? Do I have to
use weighted expressions to calculate the 'delta_[<color>|colmap]'? 
Perhaps is brighter more bad than dimmer?

Thanx for your replies.



-- 


   Michael Janich, Uni Paderborn, United Germany