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From: barry@aurora.UUCP (Kenn Barry)
Newsgroups: comp.sys.amiga
Subject: Re: IFF
Message-ID: <794@aurora.UUCP>
Date: Thu, 16-Jul-87 02:00:29 EDT
Article-I.D.: aurora.794
Posted: Thu Jul 16 02:00:29 1987
Date-Received: Sat, 18-Jul-87 04:44:26 EDT
References: <954@gryphon.CTS.COM>
Organization: NASA Ames Research Center, Mt. View, Ca.
Lines: 36
Keywords: apple IBM compuserve bozos
Summary: More on GIF graphics format.

In article <954@gryphon.CTS.COM>, richard@gryphon.CTS.COM (Richard Sexton) writes:
>I just notived in todays Computer Graphics Today that compuserve Inc has
>defined an interchangable graphics format (GIF) to allow Mac's and IBM's
>and other computers to exchange pictures. They go on to note that GIF
>readers are also available for the Amiga and ST's.
>Is there some reason they did'nt use IFF ?

	Why, because Amiga is an oddball machine whose existence isn't
even acknowledged by the Big Guys, of course ;-).
	But, seriously, folks... I've downloaded the GIF software and
some pics from Compuserve, and it does have one great advantage over
IFF: the same picture is a much smaller file when GIF encoded than IFF
encoded - anywhere from 1/2 to 1/8 the IFF size. When you're downloading
at 1200bps at Compuserve's exorbitant hourly rates, that's a big plus.
	I noticed in the docfile for it that it supports huge
resolutions, too - over 16K X 16K, I presume for the purpose of encoding
pics intended for a laser printer. Does IFF support this? I know, don't
answer, I should read the manual.
	One real stupidity of GIF, though. The maximum # of colors
supported is 256 (somebody's wearing IBM-trademarked blinders). The
conversion software for converting Amiga's IFF pics to GIF doesn't
understand HAM at all; it doesn't cut the # of colors down, it just
ignores the HAM flag and screws up the colors completely. If you've ever
tried viewing a HAM pic with one of the old 'show' utilities that didn't
understand HAM mode, you've seen what the resulting picture looks like.
As for going the other direction: I haven't found any pics on
Compuserve, so far, that use more than 16 colors, so I don't know what
the Amiga's GIF software would do with a 256 color pic. What it should
do, ideally, is convert it to HAM mode, of course; what it probably
actually does is reduce the # of colors.

-  From the Crow's Nest  -                      Kenn Barry
                                                NASA-Ames Research Center
                                                Moffett Field, CA
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