[Gdal-dev] BigTiff and libtiff

[Garrett Potts]

Hello:

Just sent the bug report on Bugzilla.

Thank you for the time on this.  Have a good day.


Take care

Garrett

On Sep 17, 2007, at 1:44 AM, Andrey Kiselev wrote:

> On Sun, Sep 16, 2007 at 12:12:31AM -0400, Frank Warmerdam wrote:
>>> It is not correct. Take a look at TIFFDirEntry structure in  
>>> tiffiop.h,
>>> it has 64-bit tdir_count field. There is a link to specification:
>>>
>>> http://www.awaresystems.be/imaging/tiff/bigtiff.html
>>>
>>> We certainly need large counts for strip/tile indexing, so it is.
>>
>> Note that Garrett is talking about the number of directories, not the
>> count of values in a tag which is what tdir_count is.
>
> Er, right, I have misread it.
>
>> I believe the directory index is a uint16 in the libtiff api
>> (TIFFSetDirectory(), etc), but the file format just uses a chain of
>> directions and has no explicit list on the number of directories, nor
>> use of directory numbers or ids.
>>
>> I still can't fathom why anyone would want more than 64K directories
>> in a TIFF chain, but if so, I don't see why the libtiff api couldn't
>> be changed to use at least "int" for this in libtiff4.
>
> The maximum number of directories is only limited by the maximum
> directory offset, so in theory we can have more than 2^32 IFDs in
> BigTIFF. So it is better to go with uint64 instead of int.
>
> Also the format does not use dirlist, but libtiff does and this change
> should be carefully reviewed.
>
> Garrett, please, create the bug report in libtiff's Bugzilla on this
> issue.
>
> Best regards,
> Andrey
>
> -- 
> Andrey V. Kiselev
> ICQ# 26871517
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