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From: minow@mountn.dec.com (Martin Minow)
Newsgroups: comp.sys.mac.programmer
Subject: Dissolve bits subroutine caution.
Message-ID: <203@mountn.dec.com>
Date: 30 May 89 11:58:28 GMT
References: <5638@hubcap.clemson.edu>
Reply-To: minow%thundr.dec@decwrl.dec.com (Martin Minow)
Organization: Digital Equipment Corporation
Lines: 20

In article <5638@hubcap.clemson.edu> mikeoro@hubcap.clemson.edu
(Michael K O'Rourke) asks about a library implementation of Mike
Morton's dissBits code.

Watch out: dissBits gets its speed by writing the screen directly.
It will not work on a color monitor, and shortly after you run the
demo programs, your system will strongly desire to be rebooted.

A fast dissolve-bits subroutine that worked well with all Mac monitors
-- and followed the Mac programming guidelines -- would be nice, but
Mike Morton didn't write it (nor did he claim to).

For what it's worth, on a Mac SE, inverting one pixel using MoveTo
and Line requires almost 1 millisecond.  Inverting one pixel by writing
directly to the screen takes about 30 microseconds.  (All code written
in C.)  I.e., a fast dissolve routine that only uses toolbox calls
and works on all Mac screens hasn't been written yet.

Martin Minow
minow%thundr.dec@decwrl.dec.com