[Digikam-users] IPTC handling and limits

Gilles Caulier caulier.gilles at gmail.com
Wed Sep 12 21:18:08 BST 2007

2007/9/12, Thomas Hummel <hummel at pasteur.fr>:
> On Wed, Sep 12, 2007 at 03:24:07PM -0400, Gilles Caulier wrote:
> > yes, in theory. For JPEG, the IPTC  section is limited to 64Kb. for PNG
> and
> > TIFF, there is no limit.
> sorry if I misunderstand, but here you mean, by keyword (like one line of
> my exmaple below (people/family/thomas) or for the whole ?
> > To be clear, if in digikam I assign, for a picture the following flags :
> > >
> > > people/family/thomas
> > > people/family/laurence
> > > animals/cats/timi
> > > ...
> > > can I have any number of those saved in IPTC keywords as long as each
> of
> > > them (such as people/family/thomas) is less then 64B long ?
> > yes
> Same clarification request as above : here you mean "yes" whatever the
> file
> format (jpeg, tiff, ...) or just for some of them ?

IPTC metadata format is undependant of file format, excepted about where
picture store the IPTC byte array and which size restriction is relevant.

in IPTC you can store an unlimited list of keywords, of 64B each (nx64B)

> all tags are stored in digiKam DB. when all will be ready in 0.10, just
> use
> > the sync pictures<->DB tools  to update all in your images. Of course
> the
> > future right options to sync XMP must be enable (XMP config panel not
> yet
> > done).
> Ok, I see, but that would be an argument for creating tags with accents
> (UTF-8)
> right now, wouldn't it (so tags name are here to stay and won't need to be
> "accentuated" later) ? Is the patch you mention below activated by default
> ?

the pach is not yet apply in source code.

To be clear :
> Do I have better to create right now a tag named "Françoise", in order not
> to
> rewrite "Francoise" into "Françoise" when XMP will be supported ? Or is it
> safer, regarding the status of char-encoding right now, to create
> "Francoise"
> and then "migrate" it later when the "ç" will be supported (but I cannot
> think
> of any easy way to do it automatically) ?

DB store all strings in UTF-8. When you store tags as IPTC keywords, all
char are converted to ascii latin1 format.
You create all you tags using accents as well, but you must take a care than
IPTC will not support it very well. If you is patient, XMP support will be
available for 0.10 planed for KDE4 release.

I don't know a simple way to patch all tags to add accents automaticly. You
can certainly do it with a script which will make changes in SQlite DB file.

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