Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!mcsun!unido!fauern!immd4.informatik.uni-erlangen.de!mlelstv
From: mlelstv@immd4.informatik.uni-erlangen.de (Michael van Elst )
Newsgroups: comp.sys.amiga
Subject: Re: a "mirror image" blit
Message-ID: <550@medusa.informatik.uni-erlangen.de>
Date: 20 Oct 89 09:42:04 GMT
References: <1646@nigel.udel.EDU> <58.filbo@gorn.santa-cruz.ca.us>
Organization: IMMD IV, University of Erlangen, W-Germany
Lines: 21

filbo@gorn.santa-cruz.ca.us (Bela Lubkin) writes:

>In article <1646@nigel.udel.EDU> Alexander Hinds writes:
>>What I need to do is take source bitmap, and blit its mirror image
>>into the destination bitmap.  Now I know this can be done with low-level
>>bliter calls, but I can't seem to figure out quite how to do it.

>Is this possible?  My reading of the hardware manual suggests it is not.

It won't be possible. The blitter can't address one bitmap in ascending
order and the destination bitmap in descending order ! It can't swap
bits in a word either.

The fastest way should be a table of 65536 mirrored words and convert each
bitmap word through this table. If you have to place the mirror at a different
place or it's not a multiple of words wide you have to shift the words to
a new position. This task is easily handled with the BltBitMapRastPort routine.

				Michael van Elst

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