2006.08.25 15:56 "Re: [Tiff] IPTC tag", by Joris Van Damme
This IPTC tag discussion seems to be a lot of heat about something which can not be repaired. The horse has already left the barn. Elvis has left the building.
I do agree. I tried to express more or less the same when I mentioned the breathing apparatus. I should have remembered to mention Elvis instead. ;-)
In GraphicsMagick we deal with the long-swapping issue by simply swapping when necessary (when TIFFIsByteSwapped() returns true). The length of the data is always assured to be evenly divisible by four. This approach seems to work.
As far as I can tell from that which has been said already, your approach would not be failproof either. Interestingly, it will fail on likely about the same files that are not supported in Photoshop. You would be able to generate such a file easilly, by writing any long IPTC data, directly with TIFFSetField in LibTiff, on a file with byte order different from machine byte order.
As you say, though, Elvis has...
IPTC data is found in TIFF using several different mechanisms. Photoshop stores IPTC data in its own (8BIM) chunk so the same (or different) IPTC data may appear in a TIFF a couple of times.
See, even though Elvis did leave, there are still people who do things with this data. So I'm left thinking comments like you make here, should go someplace where people find 'm, as in, dedicated IPTC tag page over in the tag dir.
Joris Van Damme
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