Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!WATDCS.BITNET!DMIHOCKA
From: DMIHOCKA@WATDCS.BITNET (D Mihocka)
Newsgroups: comp.sys.atari.st
Subject: (none)
Message-ID: <8803180139.AA04570@ucbvax.Berkeley.EDU>
Date: 17 Mar 88 18:46:04 GMT
Sender: uucp@ucbvax.BERKELEY.EDU
Organization: The Internet
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RE: 512 COLOR DISPLAYS.
512 Color Displays

To Wayne Knapp:

The methods you describe are pretty well what Spectrum uses. During the
vertical blank, it waits until the first scan line, then just starts
blasting into the color registers for about 13 ms, then exits the VB.
This leaves the user process a  couple of ms before the next VB.
Writing the Spectrum display routine is rather easy. I wrote a slideshow
program in Megamax C that displayed Spectrum files, and other slideshow
programs are now starting to incorporate that feature too. All I did was
disassemble the Spectrum slideshow. The code is a lot simpler than you
might imagine. Just look for the MOVE.L (An)+,(An)+ instructions (about
24 in a row) and that's the main loop of the display routine.
The file format was released about 4 months ago on various places like
Compuserve and such (both the SPC and SPU formats). With a slight modification
to the Spectrum display routine, I was even able to get medium rez displays
(i.e. 640x200 in 512 colors) and even split screen resolution changes within
the same Spectrum picture (see my slideshow and you'll see what I mean).
You're on the right track. I suggest you download the file format off
Compuserve or GEnie, then disassemble the Spectrum slideshow program and
in a couple of hours you'll be done (writing it in C sped up development
time quite a bit).
About releasing the code P/D. I don't know about that. If Antic had wished
the display routine to become P/D, I'm sure they would have published an
article in START or something. They have only published the file format, _not_
the display routine. I'd check with them if I were you. I don't know what
Antic's attitude is abot people using it in their programs. They certainly
haven't complained about the other slideshow programs and I plan to use the
routine (my modified 640x200 routine) in the title page of an upcoming
program that I'll be releasing shareware.
Would anyone care to comment of whether or not using a Spectrum-like display
routine is a copyright infringement?

- Darek

CIS: 73657,2714
Delphi: DAREKM
GEnie: DAREKM
BIX: darek