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December 2004
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2004.12.07 04:13 "Re: Having problems adding IPTC to a TIFF", by Bob Friesenhahn
On Tue, 7 Dec 2004, Joris wrote: > > - The specification says that the IPTC data contains data of different bitsizes > (byte, word, long, and undefined at the tag container level but anything on the > IPTC tag level) Which specification in particular are you using? IPTC NewsPhoto record is very old (early 90s) and last I checked (couple of years ago), it seemed that IPTC had pulled the spec for IPTC NewsPhoto as implemented for RichTIFF. I did find a bit of information at "http://home.earthlink.net/~ritter/tiff/richtiff.html". The last paragraph is most interesting. It seems that Photoshop has implemented IPTC NewsPhoto the way you don't like it and the author of the web page sees that as a bug. As we know, Photoshop is the dominant application in this market so it is quite influential. Photoshop embeds IPTC in its own TIFF record so IPTC data can appear multiple times in one TIFF file. It seems that RichTIFF says that IPTC data can appear twice. I found a specification for RichTIFF (and something called "Solo JFIF") at http://www.mtwphoto.com/garganey/. The document provides quite a bit of history behind the format. The tag is described as being type BYTE: Tag = 33723 (83BB hex) and 34152 (8568 hex) Type = BYTE N = length of IPTC data block in bytes I agree with most of your arguments except that it is necessary to balance technical correctness against what the industry is primarily actually doing and what libtiff users are currently expecting. Bob ====================================== Bob Friesenhahn bfriesen@simple.dallas.tx.us http://www.simplesystems.org/users/bfriesen