[Digikam-devel] Storage of digiKam Tags path (again)...

[Gilles Caulier]

After investaguations, i can said than Exif is not the good place to do it.

IPTC/IIM sound fine to store this data, especially because storing Exif to
TIFF/DNG file is the hell with libtiff (Andreas, i'm waiting to have Exiv2
TIFF writting (:=))))... but libtiff can store IPTC very well.

Other stuff is to convert pictures using ImageMagick. Like ImageMagick use
libtiff internally, we can only use IPTC to not lost these data...

I will store a zlib compressed byte array of XML data (not real XMP, just an
simple XML schema to store digiKam properties).

I have take a look witch IPTC/IIM tags are free for use, reading ExifTool
database and others web page.

The "Iptc.Application2.0x00ff" sound good. Like IPTC will not be used
anymore with new photo management application, the chance to have this tag
used by another software is very limited.

This is an example of the content of the uncompressed tag :

<!DOCTYPE XMLImageProperties>
<imageproperties version="1" client="digikam" encoding="UTF-8" />
<properties comments="Ceci est un test en utilisant des caractères
accentués..." rating="4" date="2006-11-23T13:36:26" >
 <tagslist>
  <tag path="Communications" />
  <tag path="aaa/bbb/ccc" />
  <tag path="bbb/ccc/ddd" />
  <tag path="bbb/ccc/ddd/Paris" />
  <tag path="bbb/ccc/ddd/Paris/bjwdfkjhjbdqjfihbdqfdwbf" />
  <tag path="City" />
  <tag path="City/London" />
  <tag path="City/New York" />
  <tag path="City/Paris" />
 </tagslist>
</properties>

For this example the compressed data use only 374 bytes in the tag. It's
small (better than XMP can use for the same content)

What do you think about ?

Gilles


2007/3/12, Gilles Caulier <caulier.gilles at gmail.com>:
>
> Right. Thanks for this tips. I will do some investigations.
>
> Gilles
>
> 2007/3/12, Andreas Huggel <ahuggel at gmx.net>:
> >
> > On Monday 12 March 2007 00:29, Gilles Caulier wrote:
> > > Andreas,
> > >
> > > if you talking about Interroperability directory, witch tag number
> > > you recommend to use ?
> > >
> > > In Exiftool database, i can see 5 tags :
> > >
> > > 0x0001, 0x0002, 0x1000, 0x1001, and 0x1002.
> > >
> >
> > The Exiv2 taglist has the same 5 IOP tags. The Exif standard actually
> > only has tag 0x0001. Thus, the good thing about this directory is that
> > it's not widely used, so there is less potential for a conflict; choose
> > a random number and chances are good that nobody else will use the same
> > tag. On the other hand, maybe because the IOP directory is not widely
> > used, there is a possibility that it is not well supported by other
> > software. So you may want to test if applications that attempt to write
> > Exif tags manage to write the IOP directory as well.
> >
> > -ahu.
> > _______________________________________________
> > Digikam-devel mailing list
> > Digikam-devel at kde.org
> > https://mail.kde.org/mailman/listinfo/digikam-devel
> >
>
>
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