[Digikam-devel] Image Metadata extraction : implementation progress...

[Caulier Gilles]

Le Mercredi 1 Mars 2006 17:15, F.J.Cruz a écrit :
> El Martes, 28 de Febrero de 2006 14:08, Gilles Caulier escribió:
> > Le Mardi 28 Février 2006 12:22, F.J.Cruz a écrit :
> > > Of course,I'm very interested on metadata support in digiKam,
> > > especially NEF files since I'm owner of a D50.In fact, along this last
> > > week I've been having a look to exiv2 code and I want to make you some
> > > questions:
> > >
> > > - How are you going to implement metadata infor for files that are not
> > > implemented in exiv2 yet?
> >
> > The better way that i have identifed to add better RAW file support is to
> > re-use implementation from ExifProbe project :
> >
> > http://www.virtual-cafe.com/~dhh/tools.d/exifprobe.d/exifprobe.html
> >
> > I think that only a simple exif/markernote extraction is enought in
> > digiKam at this moment.
> >
> > > Actually exiv2 has support only for CRW files
> > > (one of the two Canon RAW formats, the other one is CR2), altough there
> > > are files with makernotes specifications for a lot of manufacturers, so
> > > if I want to implement metadata extraction for NEF files, have I to
> > > implement the equivalent to crwimage in Exiv2? this can be a hard work
> > > if we have to do this for all the manufacturers who provide RAW format.
> >
> > The ExifProbe have a very well documentated source code about. Each file
> > format is separated cleanly. I think we can trying to use it.
> >
> > Each Digikam::DMetadata::loader are separate too. We can add new image
> > file format loader progressivly without any risk.
>
> I want to write this stuff for nef files, but I need you give me some tips
> about how to implement it (following the ideas  you described up)
>

Well to start, i will use the code from this program :

http://pages.quicksilver.net.nz/pepe/d70/Nikon_D70_on_Linux.html#exif

the file http://pages.quicksilver.net.nz/pepe/d70/neftags2jpg.tar.bz2 is a 
small c implementation witch uses exiv2 ! It's extract any tags from a NEF 
file and contruct an Exif data container using Exiv2.

You need to backport this code and put it on a new file to link with the 
dmetadata::rawloader.

You can certainly get more tags using ExifProbe implementation, but you need 
to study  ExifProbe implementation. It's more complicated.


> > > - What's about "write-access" on iptc data?
> >
> > With Exiv2 you can write IPTC tag in image, CRW included.
> >
> > > - Which of all  these changes are for 0.9.0?
> >
> > Right question. I need any report about my patch with the current
> > implementation before to commit anything.
>
> About the new exif/makernotes/iptc viewer looks fine but there is a lot of
> work to do and not only for other raw files. There is some fields and a lot
> of values that are not in "human-readable" format so we need  a
> "dictionary" to translate this stuff to something that anybody can
> understand. If we have exiftool as reference, you can understand what I'm
> talking about.
>
> So if you give me some tips, as I've said, I can start to implement
> metadata stuff for nef files (or other files format you want), until we
> have a final decision about color management issue.

Yes i seen. Look like Exiv2 author have send any tips on the ML to improve 
this problem. I will fix it.

Gilles