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December 1996
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1996.12.11 18:31 "Re: Confusing TIFF Tags", by Sam Leffler
To: tiff@sgi.com
Subject: Confusing TIFF Tags
Date: Wed, 11 Dec 1996 13:01:35 +1100
From: Hugues Talbot <Hugues.Talbot@dms.csiro.au>
Hello All,
I'm confused by (at least) one thing in Sam's library.
Some tags, like the SampleFormat tag (#339), which help interpret
each data sample in a pixel, should be associated with as many
values as there are samples per pixel, according to TIFFv6.0
Yet Sam's library allows to retrieve only one value for
this tag per subimage, regardless of the number of samples.
The TIFFGetField function should return an array of values, not
a single one.
There are other examples, like SMinSampleValue, SMaxSampleValue,
etc.
Is this a known libtiff limitation or is this a policy? in any case
where can I find some documentation about these puzzling facts ?
The library does not support certain tags in their most general
form. Examples are the above, Compression, MinSampleValue,
MaxSampleValue, and BitsPerSample. SamplesPerPixel is documented in
libtiff(3T); I can't recall where the restrictions on the other
tags are documented.
If you believe it is important to support per-sample values for
any of the tags the library currently restricts then feel free
to provide the necessary changes to the library+documentation.
Sam