Path: utzoo!utgpu!water!watmath!clyde!bellcore!faline!thumper!ulysses!andante!princeton!udel!rochester!cornell!blandy
From: blandy@cornell.UUCP
Newsgroups: comp.sys.amiga.tech
Subject: Re: bitmaps with intuition...
Summary: Bitmaps aren't necessarily consecutive
Message-ID: <18336@cornell.UUCP>
Date: 15 Jun 88 14:06:08 GMT
References: <4370@gryphon.CTS.COM> <3170@charon.unm.edu> <211@hor-res.UUCP>
Sender: nobody@cornell.UUCP
Reply-To: blandy@marduk (Jim Blandy)
Organization: Cornell Univ. CS Dept, Ithaca NY
Lines: 20

In article <211@hor-res.UUCP> berry@hor-res.UUCP (No comment) writes:
>this case) x,y pixel value. The planes are stored sequentially in memory.
>Plane 1 first (8K), then plane 2 (8K more) and then plane three. So for
>our example, to display pixel 0,0 you would start at bitmap[0] combine it
>with the pixel 8,000 bytes away at bitmap[8000] and then finally with
>bitmap[16000]. This would get you the Value of the color register that
>will be displayed as the pixel color when the Amiga displays this pixel.

Uh, I may be wrong, but are the bitmaps GUARANTEED to be stored
one after the other in memory???  If you're lucky in allocation, they
might be.   The BitMap structure contains an array of pointers to the
tops of the bitplanes; if b is a BitMap, b.Planes[0] points to the
first bitplane, b.Planes[1] to the second, etc.  I think you'd be
better off using that...

Or am I wrong?
--
Jim Blandy - blandy@crnlcs.bitnet
"insects were insects when man was just a burbling whatsit."  - archie
How necessary ARE disclaimers, anyway?