2006.01.10 07:41 "[Tiff] Incorrect IFD???", by Thomas Oldenkott

2006.01.10 08:03 "Re: [Tiff] Incorrect IFD???", by Joris Van Damme


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But when I create an multipage tiff image with the lifftib library I get other values at this postion.

I think the key word here is 'at this position'. TIFF is differently from most other image file formats, in that it has no fixed order or position of data blocks. For instance, inside the file header, which is the only fixed positioned structure, is an offset to a first IFD. This can be 8, as is the case in your first 'correctly imported' example. In that case, you'll be seeing tag count of first IFD at position 8. It can however also be 25244, in which case you'll be seeing that exact same tag count at position 25244, but something totally other and unrelated at position 8. This is the case with your second 'created with libtiff' example.

Does this clearify the issue for you? If you want to read a more complete informal overview of these highest level structures, I recommend http://www.awaresystems.be/imaging/tiff/faq.html#q3.

Joris Van Damme
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