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From: Gary McGath <gary@hulmail.harvard.edu>
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Date: Wed, 29 Dec 2004 10:15:21 -0500
To: tiff@remotesensing.org
Subject: [Tiff] Re: how to insert or replace a image in multi-page tiff
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<yourpattern@126.com> wrote:


> As an addition, it would be logical for empty IFDs to be created if
> the
> requested pagenumbers is greater than the current number of images in
> the
> file. For example I want to insert an image at page 8 (start counting
> at 1)
> to a TIFF file that has only 6 images. I would end up with a IFD #6
> linking
> to an empty IFD, and this empty IFD would link to the new image at
> position
> 8.
> Do the commonly used multipage capable decoders deal with empty IFDs ?
> Are
> they legal by the spec ?


Each image type requires certain tags in an IFD.  You could make 
a case that an empty IFD signifies no image, but then I'd expect
it would just be skipped over, not that it would generate a
blank page.  A blank page is an image; with an empty IFD, you can't
even say what its dimensions are.


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