Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!mips!apple!well!smoke
From: smoke@well.sf.ca.us (Nicholas Jackiw)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Problems with color animation
Message-ID: <25759@well.sf.ca.us>
Date: 28 Jun 91 16:42:45 GMT
References: <17477@darkstar.ucsc.edu>
Organization: Whole Earth 'Lectronic Link, Sausalito, CA
Lines: 36

In article <17477@darkstar.ucsc.edu> anderson@SECS.ucsc.edu writes:

[minor epic of woe about CopyBits flicker deleted]
> 
>The size of the bitmap may be a contributing factor.  I am using the full 
>screen for the drawings so my first question is whether or not it is possible
>to do the copybits fast enough  on this large a bitmap?
>
>Gary D. Anderson

Is your offscreen bitmap at the same pixel depth as your color monitor?
If not, you might want to try determining the pixel depth of the screen
on which your drawing window appears (via the Device Manager), and then 
allocating your offscreen image as a *pixMap*, not a bitMap, at that 
depth.  This saves CopyBits from having to resize each pixel dynamically
when moving them to the screen.    You can test if this is the problem
by setting your monitor to black&white before testing your app (assuming
that your offscreen bitmap is a bitmap, i. e. is black and white). If
the flicker disappears, that's your problem.

Some CopyBits calls can take seconds to complete, even when copying
a relatively small picture.  You'll see the image rippling during these
cases.  If you don't give it too much work, though, it performs quite
well; I routinely do full-window animation with CopyBits (between
bitmaps of the same depth and bit-alignment), and never worry about
flicker, or tying my job to a vertical interrupt, etc.





-- 
                              --- * ---
Nick Jackiw                  Smoke@well.sf.ca.us   | Jackiw@cs.swarthmore.edu
Key Curriculum Press, Inc.   Applelink:KEY.EDUSOFT | (415) 548-2304
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