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

[Gilles Caulier]

Le Mardi 28 Février 2006 12:22, F.J.Cruz a écrit :
> El Martes, 28 de Febrero de 2006 11:09, Gilles Caulier escribió:
> > Hi all digiKam users/team,
> >
> > Like you have seen last week, I have started a new implementation of
> > metadata viewer using libExiv2 instead the current Exif viewer using
> > libkexif.
> >
> > A fresh screenshot can be seen here :
> >
> > http://digikam3rdparty.free.fr/Screenshots/digikam0.9.0-alpha6.png
> >
> > After any days of indeep testing, the implementation is more mature. Like
> > you can see in this screenshot, we have :
> >
> > - A standard Exif metatada viewer.
> > - An Exif  Maker Notes viewer
> > - An IPTC metadata viewer.
> > - Support of CRW metadata (thanks exiv2)
> > - Support of Raw profiles embedded (Exif/IPTC) in PNG files built by
> > ImageMagick during JPEG -> PNG conversion.
> > - Each sidebar tab can be filtered to "Simple" (user friendly: the more
> > important for photograph) and to "Full" (all metadata).
> > - All metadata groups are more visible than old Exif viewer.
> >
> > The implementation is based on 2 parts :
> >
> > -> One metadata extractor witch detect the file type and use a dedicaced
> > loader to construct Exiv2 metadata container. Actually JPEG, PNG and CRW
> > files are supported. I have planed to do TIFF/DNG files and any others
> > RAW files like NEF (Paco if you is interresed (:=)))) and MRW. The
> > implementation is similar to Digikam::DImg container (about loader)...
>
> 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.

>
> - 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.

Gilles