Path: utzoo!attcan!uunet!sjsca4!greg
From: greg@sj.ate.slb.com (Greg Wageman)
Newsgroups: comp.sys.atari.st
Subject: Re: spectrum and quantumpaint formats
Message-ID: <1989Nov21.222907.25142@sj.ate.slb.com>
Date: 21 Nov 89 22:29:07 GMT
References: <15@spocom.UUCP>
Reply-To: greg@sj.ate.slb.com (Greg Wageman)
Organization: Schlumberger ATE, San Jose, CA 95110
Lines: 25

Opinions expressed are the responsibility of the author.

In article <15@spocom.UUCP> gng@spocom.UUCP writes:
>
>Some more quick questions - Does anyone have information as to how spectrum
>and quantum paint programs are able to make the ST display more colours than
>usual?  I'm especially bewildered as to how quantum paint can display
>3375 colours or more!  Any info appreciated...

Spectrum 512 works by using the CPU to reload the hardware palette
registers during the current scan line.  An initial palette is loaded
during horizontal retrace; then, in a *very* tight loop, each register
is loaded in sequence with a new color from the Spectrum palette.
Since each register is reloaded twice in the scan line, a total of 48
different colors are possible in one line.  In addition, since there
is an independent palette for each scan line, all 512 colors may
appear within one screen.

I don't know how Quantum Paint works, but I suspect they use some
variation on this scheme.

Copyright 1989 Greg Wageman	DOMAIN: greg@sj.ate.slb.com
Schlumberger Technologies	UUCP:   {uunet,decwrl,amdahl}!sjsca4!greg
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