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From: clunie@ohsuhcx.ohsu.edu (David)
Newsgroups: comp.graphics
Subject: Re: Trouble with TIFF format
Message-ID: <840@ohsuhcx.ohsu.edu>
Date: 10 Dec 90 22:38:32 GMT
References: <1990Dec5.183212.29252@msuinfo.cl.msu.edu>
Reply-To: clunie@ohsuhcx.UUCP (David)
Organization: Oregon Health Sciences University, Portland
Lines: 21

I have not played with libtiff in a while, but I seem to remember that any
thing that uses this library, which includes most sun stuff, I think
even including Sun's own sunvision product, fails on a lot of tiff files
imported from the mac and pc world. The reason being that many mac 
based programs ignore the recommendation in the Tiff specification that
says one should try not to output entire images as one long "strip" in
tiff parlance. These programs (and I hate to admit, some of my own) take
a shortcut by owriting a single StripOffset tag into the IFD with its value
being a pointer to the start of the entire image. They may not even bother
writing a StripByteCount tag. My interrpretation of the standard is that
this is legal, though not recommended.

What the unknown tag is, I don't know, presumably it is something the scanner
manufacturer has allocated for his own use.

I have posted this rather than mailed it to you, in the hope that other people
using the tiff format may care to comment on this practice of writing one
long strip, and whether or not libtiff should support it (if this is indeed
the problem here).

Regards ... David Clunie (clunie@ohsu.edu)