2011.02.10 16:49 "Re: [Tiff] ImageDepth tag", by Frank Warmerdam

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,
 --

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