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From: jgk@osc.COM (Joe Keane)
Newsgroups: comp.arch,comp.graphics
Subject: Re: Resolution, etc.
Summary: How many colors do you really need?
Keywords: colors, resolution, dithering
Message-ID: <4023@osc.COM>
Date: 20 Nov 90 21:40:37 GMT
References: <240@csinc.UUCP> <1990Nov15.052925.1265@imax.com> <2928@crdos1.crd.ge.COM> <1990Nov16.190248.20437@ux1.cso.uiuc.edu>
Reply-To: jgk@osc.COM (Joe Keane)
Followup-To: comp.arch
Distribution: na
Organization: Versant Object Technology, Menlo Park, CA
Lines: 33

In <2928@crdos1.crd.ge.COM> davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr)
writes:
>  I'm not convinced that you need 24 bits of color for the memory,
>either. Systems like the VGA which have a large palette and a limited
>number of selections work very well. If you look at the output of a 24
>bit color scanner scanning quality photographs, you rarely find an image
>which doesn't map into 256 colors nicely. Very rarely.

In article <1990Nov16.190248.20437@ux1.cso.uiuc.edu> msp33327@uxa.cso.uiuc.edu
(Michael S. Pereckas) writes:
>Note that this gets to be a mess in a hurry if you want to put two
>different images on the screen at once (perhaps in separate windows).
>Pallets can be a problem in multitasking, windowing environments.

I agree, pallettes are a big pain.  A true-color display is a lot easier to
deal with, since there's no global interaction between pixels.  Or you can
agree once and for all on a single pallette, which all windows on the screen
have to use.

Let's assume we have graphics software that understands the concept of
dithering, not like some other software we could mention.  So when you say to
fill a rectangle with a given color, it actually fills it with some neat
pattern alternating between a few colors, such that the overall color is very
close to what you asked for.  Assume that this software is actually competent
at what it does, so that there are no nasty artifacts and the boundaries
between colors work out right.

Now also assume we have a display with good resolution, so the individual
pixels are quite small.  So then, how many colors do we need?  In other words,
what is the largest color difference between neighboring pixels such that it
won't be obvious that the pixels are different colors?  It seems to me that
it's somewhere around 4 bits per component, for a total of 4K colors.  Maybe
this is a little low, though.  What do you all think?