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February 2011
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2011.02.10 17:23 "Re: ImageDepth tag", by Edward Grissom
I could not find mention of the ImageDepth tag at http://www.awaresystems.be/imaging/tiff/tifftags/search.html Does anyone have a reference description for this tag ? Thanks. -- ed grissom ed.grissom@intergraph.com -----Original Message----- From: tiff-bounces@lists.maptools.org [mailto:tiff-bounces@lists.maptools.org] On Behalf Of Frank Warmerdam Sent: Thursday, February 10, 2011 10:49 AM To: tiff@lists.maptools.org Subject: Re: [Tiff] ImageDepth tag On 11-02-10 11:33 AM, John Evans wrote: > Hello, I was wondering what people's experiences are with the ImageDepth > tag. > There are a few mentions of it on this mailing list if one goes back far > enough, but every TIFF I've seen so far (that has actually had the > ImageDepth > tag set) has had ImageDepth trivially set to 1, such as "cramps-tile.tif". > Every TIFF except for one, that is. That particular TIFF was pretty > simple > otherwise, photometric interpretation of MINISBLACK, SamplesPerPixel = 1, > ImageDepth = 16. > > I can see how the ImageDepth tag could be useful, i.e. just one IFD with > thousands of slices vs. thousands of IFDs each with just one slice. And I > can create TIFFs with with ImageDepth> 1 in other photometric > interpretations, such as RGB and YCbCr... but do people ever actually run > into such beasts? John, I have not encountered TIFF files with non-trivial image depth values. I doubt there is much client software ready for them. I'm not even convinced that libtiff handles them well. In *theory* I can see some utility for ImageDepth, but in practice I would prefer to just avoid promoting it's use. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent