2018.11.04 23:35 "Re: [Tiff] Libtiff will be released soon", by Bob Friesenhahn

I see in tiff.h, lines 193,194 that ZSTD and WEBP compressions are assigned tags 34926 and 34927 respectively. These tags were already issued for other purposes as of October 2015, when I registered tags 34933 through 34936, so they will definitely be stomping over someone. Where is Adobe's response to this situation?

Also, I'd registered private TIFF tags 51159 and 51160 - should they go into the header file, or be declared by users who need them separately?

It is unfortunate that we are only hearing about this collision now, although you were aware that these features were being developed, and you were aware of the definite possibilty of a collision given the concerns you already expressed several times about the lack of a working registry.

I invite you, and anyone else to share TIFF tag numbers which were allocated by Adobe and which are now in danger of colliding with independent tag allocations. It is only necessary to know the numbers to avoid. It is highly irresponsible for Adobe to not publish a list of the numbers which have already been allocated.

Re-use of tags is only a problem if a file using the conflicting tag is opened by software which implements a feature based on that tag id.

Files written by libtiff are likely to become popular so it behooves implementors of proprietary TIFF software to try to avoid collisions.

This is the 'tiff' mailing list and not at all limited to discussions of libtiff development.

Private TIFF tags have no business in libtiff header files since libtiff does not use them. Libtiff can offer to store such information in a file in its source repository, suitably vetted to avoid any trade secret issues.

Bob
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Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/