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To: tiff@sgi.sgi.com
Subject: Re: JPEG Compression in TIFF 
In-reply-to: Your message of Tue, 12 Jul 1994 16:59:42 EST.
             <9407122359.AA04923@tazboy.JPL.NASA.GOV> 
Date: Wed, 13 Jul 1994 11:04:21 -0400
Message-ID: <17882.774111861@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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> As several others will point out, there were indeed some serious problems
> with the JPEG implementation, which have been ironed out and submitted for
> revision with the Aldus TIFF Developers. Tom Lane <tgl@cs.cmu.edu> ran a
> mailing list for dealing with this problem; you may want to contact him
> to find out the current status of the revisions (actually, I'm pretty
> curious about the status myself--Tom?).

A draft proposal was circulated back in February, and since then I've
basically been waiting for responses.  There have been darn few :-(.
I've just recently started talking to the people at Aldus about converting
the draft into official text for the TIFF standard.  Something should
emerge by the end of the summer (he says with fingers crossed).

Meanwhile, the IJG library has been undergoing a rewrite which should make
it much easier to plug together with libtiff.  Sam and I will probably
undertake that task over the rest of the summer.  Note that we will
support ONLY the new spec, not the 6.0 definition.  The old spec requires
the TIFF control layer to be much too cozy with the innards of the JPEG
codec; implementing it would require doing serious damage to both libraries.
And you'd still be left hanging concerning how to interpret the numerous
ambiguities of 6.0's section 22.

I'd be glad to send a copy of the draft proposal to anyone who asks.
It is not implementable since a tag number or two remains to be assigned,
but the important stuff is there.

			regards, tom lane
			organizer, Independent JPEG Group

PS: note I'm no longer at CMU; my address is now tgl@sss.pgh.pa.us.

