[Digikam-devel] [Bug 220545] Cannot write XMP sidecar files

Jakob Malm jakob.malm at gmail.com
Thu Apr 1 06:33:04 BST 2010


https://bugs.kde.org/show_bug.cgi?id=220545





--- Comment #10 from Jakob Malm <jakob malm gmail com>  2010-04-01 07:32:00 ---
Andreas, thanks for your reply!

(In reply to comment #9)
> Exiv2 (that without the little 'k' ;) converts a number of Exif tags and IPTC
> datasets to the XMP sidecar and back. Try it out with the exiv2 command line
> utility. 
Yes, it's a very handy tool. I guess you mean "... IPTC datasets _in image
files_ ..."? In my simple test above, the XMP encoded Exif and IPTC stuff was
returned in the XMP 'field' of the Exiv2::Image - not in the Exif and IPTC
fields, respectively, as far as I could tell. How can this be accomplished? The
case is different from what the command line utility does with the "-i X"
option in that it _only_ reads the contents of the XMP sidecar, and doesn't
have an image file to put write it to. Is it in the writing that the conversion
happens?

I suppose that at least when I would do a "save" from libkexiv2 (which puts
Exif, IPTC and XMP metadata in the Exiv2::Image using setExifData, setIPTCData,
and setXMPData, respectively, and then calls writeMetaData) the Exif and IPTC
data would get converted to XMP tags, and written to the XMP sidecar? Can you
confirm this behaviour?

> Gilles is right about the makernote, that is lost. It's also true that I'm not
> keen to dump the makernote as a large binary blob into an XMP property as
> exiftool does. It is unlikely that any other application would ever be able to
> deal with such a blob properly. Instead I suggested to write the _known_
> makernote tags as readable properties in new custom namespaces (e.g., like
> Xmp.Nikon3.WhiteBalance). But that's just an idea at this point, no such code
> exists yet.

I must say that, personally, I have no opinion about these makernotes, as I do
not know anything about them...

> > maybe I could first get reading and writing XMP sidecar files supported from a
> > menu command, and then we can see where we want to go from there?
> 
> I think that should be possible. In digiKam the main concern is about the
> workflow and the options to control the handling of XMP sidecars. 

Agreed.

> When it comes
> to the contents of the sidecar files, you'll need to turn to libexiv2. 

I'm not following... Are you talking about the issue with getting the XMP
encoded Exif and IPTC tags converted into proper Exif and IPTC, i.e. the issue
discussed at the top of this reply?

> 
> Andreas

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