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From: parkern@jacobs.CS.ORST.EDU (Neil Parker)
Newsgroups: comp.sys.apple2
Subject: Re: //gs graphics/music
Summary: Read the Tech Notes
Message-ID: <1990Nov20.042109.23588@scion.CS.ORST.EDU>
Date: 20 Nov 90 04:21:09 GMT
References: <179@generic.UUCP>
Sender: @scion.CS.ORST.EDU
Reply-To: parkern@jacobs.CS.ORST.EDU (Neil Parker)
Organization: The Universal Society for the Prevention of Reality
Lines: 27
Nntp-Posting-Host: jacobs.cs.orst.edu

In article <179@generic.UUCP> taob@pnet91.cts.com (Brian Tao) writes:
>From parkern@jacobs.CS.ORST.EDU (Neil Parker):
>> Actually, Apple Preferred Format uses the Miscellaneous Tool Set routine
>> _PackBytes ($2603) to do the compression.  _PackBytes uses a form of run-
>> length coding for compression--a bit less sophisticated than Huffman.
>    Ah yes, that's right.  I remember reading about that in SHRConvert.  So
>all you have to do is pass a few parameters to _UnPackBytes and it will
>automatically decode the APF file?  The joy of using the Toolbox!  :)

Yes, you can decode an APF picture using _UnPackBytes.  However, it isn't
quite as simple as just passing the whole file to the toolbox.  If memory
serves, each scan line is individually packed, and there are a lot of
pointers in the file to the start of each scan line.  There's also a lot of
other stuff in the file too.  I'm not kidding when I say "Read the File
Type Note"--it'll make life a lot easier for you.

>    If that's the case, I wonder if Apple will integrate some sort of built-in
>GIF encoder/decoder for QuickDraw II and the Misc. Tool Set.  Then we would be
>able to load in GIF's directly to any paint program.

Sure, it would be handy...a routine to do LZW compression (the kind used by
GIFs) would be useful for a lot of stuff, not just GIFs.  However, I
wouldn't advise holding your breath in anticipation...
--
Neil Parker                 No cute ASCII art...no cute quote...no cute
parkern@jacobs.cs.orst.edu  disclaimer...no deposit, no return...
parker@corona.uoregon.edu   (This space intentionally left blank:           )