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From: logajan@ns.network.com (John Logajan)
Newsgroups: comp.sys.atari.st
Subject: Re: Graphics on the STE - v. generally speaking...
Message-ID: <1991Apr3.055519.2322@ns.network.com>
Date: 3 Apr 91 05:55:19 GMT
References: <1245@exua.exeter.ac.uk> <1991Apr3.004047.511@jato.jpl.nasa.gov>
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hyc@hanauma.jpl.nasa.gov (Howard Chu) writes:
>>4)	Is it possible to get Gif images to look remotely nice on a STE?
>
>Well, it's fairly simple to display a full 256-color GIF image, if that's
>what you mean. I have code doing this in my port of Fractint 12. Using
>frame-swapping to (almost) double the number of bits per pixel just about
>squares the number of colors to choose from, and also squares the number
>of colors displayable at once.

I take it by frame swapping that you build two (or more) logical screens
and alternate between them every vertical retrace -- so as to layer 
intensities on top of one another.  Thus your eye and the persistence
of the phosphors become the brightness integrators.  A duty cycle kind
of thing.  Let's see per color you have one frame-pixel full on and
one frame-pixel in one of 8 possible levels.  Or one at level 6 and
the other in 7 possible levels, etc .. 8+7+6+5+4+3+2+1=36 levels per
color, or 46,656 possible colors to choose from.
 
Hmm, but you still only have 16 pallette cells to choose from per
scan line, and you can only add them and not multiply them.  Giving you
32 colors per scan line  (or scan zone in Spectrum 512 mode) max.

My guess would be that flicker and pseudo-shadow movements would be
quite severe. So how does it really look?

-- 
- John Logajan @ Network Systems; 7600 Boone Ave; Brooklyn Park, MN 55428
- logajan@ns.network.com, 612-424-4888, Fax 612-424-2853