[gdal-dev] TIFF tag 33723 IPTC metadata
gregcoats at mac.com
Thu Nov 5 10:48:39 EST 2009
When Photoshop writes a .tif file, it automatically includes TIFF tag
700 XMP metadata, and TIFF tag 33723 IPTC metadata. The TIFF utilities
tiffcp and geotifcp copy these Photoshop created .tif files. For
example, the commands below read in image1.tif, and then write
image2.tif, arranged into tiles 256x256, and include the XMP and IPTC
$ tiffcp -t -w 256 -l 256 image1.tif image2.tif
$ geotifcp -t -w 256 -l 256 image1.tif image2.tif
The (unofficial ?) web page
identifies TIFF tag 33723 IPTC as Type=UNDEFINED or 7, and yet
tiffinfo shows that the Photoshop created .tif files have TIFF tag
33723 IPTC written as Type=LONG or 4. Why this difference?
The Kakadu version 6.3.0 supports reading and writing TIFF tag 700 XMP
metadata, and TIFF tag 33723 IPTC metadata. There is no problem with
XMP metadata, but when writing IPTC metadata, kdu_expand writes TIFF
tag 33723 IPTC as Type=UNDEFINED or 7, in compliance with the
awaresystems web page.
But then I observe that tiffcp and geotifcp both report the Kakadu
written .tif has an "Incompatible type" for its TIFF tag 33723 IPTC
metadata, even though the type conforms to the awaresystems web page,
although that is different from what Adobe uses in Photoshop, and as a
result the IPTC metadata is lost, and not included in the output .tif
$ geotifcp -t -w 256 -l 256 image01_v6_3_x86_03_64.tif
TIFFFetchNormalTag: Warning, Incompatible type for "RichTIFFIPTC"; tag
Should I change the Kakadu source code so that it makes the same
mistake Photoshop makes, and identifies TIFF tag 33723 IPTC metadata
as Type=LONG or 4?
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