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TIFF and LibTiff Mail List Archive

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2004.12.02 18:07 "[Tiff] Having problems adding IPTC to a TIFF", by Roland Rabien
[...]
2004.12.07 15:26 "Re: [Tiff] AdobeDeflate (was: Having problems adding IPTC to a TIFF)", by Edward Lam
2004.12.07 20:27 "Re: [Tiff] AdobeDeflate (was: Having problems adding IPTC to a TIFF)", by Chris Cox
2004.12.07 20:50 "Re: [Tiff] AdobeDeflate", by Edward Lam
[...]

2004.12.07 20:27 "Re: [Tiff] AdobeDeflate (was: Having problems adding IPTC to a TIFF)", by Chris Cox

Speaking of Photoshop, why was AdobeDeflate created?

Because someone outside Adobe defined a flate compression value and ignored the value defined by Adobe as part of the TIFF standard.

The non-Adobe flate compression value should be read, but never written. Use the Adobe flate compression value when writing.

Chris

  • 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 can read it with any tag type, but writes as type long for compatibility with some unspecified application (and the comment has been in there a long time).

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 haven't 34152 used anywhere, and Photoshop ignores that tag number.