2006.08.29 15:47 "Re: [Tiff] IPTC tag", by Joris Van Damme

Chris,

Again, if LibTIFF byteswaps IPTC data, that is a bug.

With all that is said, I think we are beginning to converge to a common opinion as to the current state of affairs. I do think we are also close to an agreement as to what should be the semi-official recommendation, as on the one hand we agree that the undefined datatype is the actual single really correct datatype, we know that Photoshop accepts it in all circumstances from your explanation, and on the other hand I am beginning to realize some people will just really need to continue writing the long datatype no matter what, since they specifically really need compatibility with software that can take none other. Your experience and Bob's seems to indicate that of the four possible states I elaborated upon, only two seem common out there, and Bob contributed an easy and obvious way to make sure LibTiff users end up doing either of those two, using TIFFIsByteSwapped to ensure that the number of byteswaps is even in all reading and writing circumstances.

I'll append my proposal for recommendation accordingly, and publish it on the IPTC tag page shortly.

So, I'm almost tempted to not respond to your comment 'is a bug'... For what it's worth, very briefly because it doesn't really matter, I don't think it is. Reading or writing data from or into tags, LibTiff takes care of byteswapping and ensures the application level need to be concerned with machine byte order data only. That is a logical feature, as well as useful and well documented. I don't think that level of functionality should actually check the tag code and make exceptions for some... The hack that is necessary here, ought to happen elsewhere, application level if no other place is suitable as is the case in LibTiff. So the actual 'bug' is completely and only the usage of wrong datatype for this tag. But this is merely my opinion, and it doesn't make a difference as to recommendation, so my dissagreement with your use of the word 'bug' is academical at best, it doesn't matter.

Thanks to you and Bob and all who helped shed light on this issue.

Best regards,

Joris Van Damme
info@awaresystems.be
http://www.awaresystems.be/
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