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From: Phil Harvey <phil@owl.phy.queensu.ca>
Subject: Re: [Tiff] EXIF JPEG Thumbnail in TIFF
Date: Mon, 2 Apr 2007 11:24:01 -0400
To: Joris <joris.at.lebbeke@skynet.be>
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Status: RO

Thanks Joris,

Your comments are useful.  At least it is now clear that
libtiff can't be used to process these thumbnails.  So
at the very least, it means that you can't use libtiff
to process EXIF information in JPEG images, which is
unfortunate.

I re-read the EXIF specification.  It does clearly
state that compressed JPEG thumbnails are not allowed
if the primary image is uncompressed (section 4.5.5
of the EXIF 2.2 specification, page 12), which could
rule out a majority of TIFF images, but as far as I
can see they should be allowed in compressed TIFF images.

Either my understanding of the EXIF specification is
wrong, or maybe it is just that this technique just
never caught on.

- Phil



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