Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!munnari.oz.au!labtam!graeme
From: graeme@labtam.labtam.oz (Graeme Gill)
Newsgroups: comp.graphics
Subject: Re: Color quantization ideas: To histogram or not to histogram, comments?
Summary: URT allows many channels
Keywords: graphics quantization
Message-ID: <10517@labtam.labtam.oz>
Date: 8 May 91 03:28:06 GMT
References: <606@lysator.liu.se> <10480@labtam.labtam.oz> <610@lysator.liu.se>
Distribution: comp
Organization: Labtam Australia Pty. Ltd., Melbourne, Australia
Lines: 30

In article <610@lysator.liu.se>, zap@lysator.liu.se (Zap Andersson) writes:
> render the spaceship with an alpha channel and overlay separately with
> an intelligen quant software, and I agree totally. But IS there some
> intelligent overlay-32-bit-images-with-different-criteria-of-importance-
> while-qiantizing-to-8-bit-code.c source around :-)

	That would be a good way of letting the renderer supply the information,
while still allowing the quantization to take place as a separate procedure.
(The UNIX toolkit approach is a fairly powerful one) The URT file format
allows for up to 256 channels per pixel, so it would be relatively easy
to add this to a renderer and quantizer that uses this format. By convention,
channels 0,1 and 2 are red, green and blue, and channel 255 is the alpha
channel.  You could choose one of the other channels to carry importance
weighting information.
	I am not convinced that it is any easier for the renderer to figure out
which objects are of interest than it is for the quantizer though. It is typical
of art that a collection of otherwise un-interesting objects will attract
ones interest when arranged, lit and viewed in certain ways. This is a purely
human interpretation.

> No, but 5 vs 6 bits makes a LOT of difference (it's just on the edge
> of what you see, especially at yucky resolutions, such as PC bleach
> 320 x 200 that I'm (semi) stuck with :-(   ((and must support))  )

	I still suggest you try out rlequant. It has consistently given me
good results where other quantizer using median cut have failed dismally.


	Graeme Gill
	Labtam Australia