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From: youngdahl@gacvx1.gac.edu
Newsgroups: comp.sys.apple2
Subject: More extended graphics on the IIgs
Message-ID: <1991Jan18.170510.1@gacvx1.gac.edu>
Date: 18 Jan 91 23:05:10 GMT
Organization: Gustavus Adolphus College, St. Peter, Minnesota
Lines: 39
Nntp-Posting-Host: gacvx1
Nntp-Posting-User: youngdahl

Well, it seems everyone agrees that at least in LIMITED usage, it is possible
to display 32 colors on at least a few IIgs scan lines by switching the
pallette and pixels on a scan line after the SCB interupt is generated, and
before the screen is refreshed.  Why do I think this is useful?  Well, its
obvious that this does nothing practical for the IIgs, as it cannot be done on
the whole screen as the "3200" mode.  But at least it COULD be used in a title
page to a program (or such) for a row of text... maybe you could shade the
letters from left to right, going through red-->blue using 32 colors??

You'd flip between:

(First half of text in colors 1-16/1st pallette)  w/ the second group of
letters not "in" the scan line's bytes

-and-

the first half of the text not in the scan line's bytes and the second group of
letters in colors 1-16/2nd pallette)


I know... its limited... but I'm just wondering if this could be done with
minimal flickering.


Also, since I'm just talking about "tweeking" the heck out of the graphics
right now, perhaps some of you have could tell me if this is possible:

Mixing 640 and 320 on a scan line.

By changing the contents of a scanline and changing its scanline
control byte from "320" to "640," couldn't one "overlay" 640 mode 80-column
text onto a background of 320-mode graphics (i.e. the advantage of 16 colors)
on at least a 1/10 of the screen?


Any comments?

Ben Youngdahl
youngdah@nic.gac.edu