2004.09.24 13:02 "Re: [Tiff] Alias Sketchbook Multi-Layer Tiff Files -- Specification", by Joris Van Damme

Suggestions on what tags to register and their semantics? Or just move over exactly what I have onto the private tags?

What tags: I don't think that's up to you to decide. I may be wrong, but I think you simply ask Adobe for private tags allocation, and they're the ones telling you what numbers.

Semantics: If you're satisfied with what is there, you're satisfied with what is there. You've already got the code, and nice documentation, so merely transplanting stuff to a newly allocated private tag without changing semantics certainly seems like least trouble. On the other hand, if you're planning a change, now is the time... And if you are, make sure to also add a version number or something to the data, so that, from this point on, you'll be able to extend things, and yet have code that painlessly detect what version tag data and thus what is there.

Obviously, I'll have to continue reading files that conform to the existing spec.

Yes, and extend the existing spec, don't just get rid of the old parts but keep them there and mark them as old. That way, when we include your specification in the documentation section of the TIFF Tag Reference, because you've got yourself legit private tags, you'll also be open about your old 'hijacking' use of TIFFTAG_HOSTCOMPUTER and such.

Joris Van Damme
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