[Digikam-devel] better metadata support : added exiv2 depency ?

Caulier Gilles caulier.gilles at kdemail.net
Tue Feb 14 19:59:04 GMT 2006


Le Mardi 14 Février 2006 16:43, F.J.Cruz a écrit :
> El Martes, 14 de Febrero de 2006 15:55, Gilles Caulier escribió:
> > Hi all,
> >
> > To support better metadata, especially Exif and IPTC, we need to use a
> > new lib. Exiv2 seem to be the better choose actually, to manipulate EXIF
> > and IPTC metadata from image file.
> >
> > http://home.arcor.de/ahuggel/exiv2/
> >
> >  Actually, Exiv2 support :
> >
> > - Exif data from JPEG files with a large suppport of special marker notes
> > from constructors.
> > - IPTC data from JPEG files
> > - Exif data from CRW RW file (Canon tm)
> >
> > In Digikam::DImg, metadata are just stored like bytes array (DImg is a
> > metadata container, no a metadata parser). It's easy to move this
> > metadata from an original image to a target image. Actually, JPEG<->PNG
> > Exif/IPTC metadata preservation is complete. If you convert a JPEG file
> > including Exif data to a PNG file using Image Editor (and vis-versa), you
> > can see the Exif metadata including to PNG file with Exif tab from main
> > interface. Look here :
> >
> > http://digikam3rdparty.free.fr/Screenshots/digikam0.9.0-alpha4.png
> >
> > Exif/IPTC are store to PNG using standard ImageMagick Raw profile tag...
> >
> > But we need more metadata preservation :
> >
> > - RAW Exif/IPTC extraction
> > ==>
> > http://www.rags-int-inc.com/PhotoTechStuff/RawStandards/RawSummary.html -
> > TIFF/EP Exif/IPTC manipulation.
> > - DNG Exif/IPTC manipulation (DNG==TIFF/EP like file. We can plan this
> > file format for the future).
> >
> > Exiv2 will support others image file format in the future, especially
> > more RAW files and TIFF/EP files.
> >
> > In all case, Extracting RAW Exif metadata is possible using
> > dcraw::parse.c method. This way is used in neftags2jpeg program dedicaced
> > to extract Exif from NEF file :
> >
> > http://pages.quicksilver.net.nz/pepe/d70/Nikon_D70_on_Linux.html#exif
> >
> > neftags2jpeg program using Exiv2 to store like a byte array Exif
> > informations (:=)))...
> >
> > In digiKam, this way can be used to make a RAW file parser to extract
> > Exif data until that Exiv2 support better RAW file format. To get a
> > complete list of RAW file tags, we can get any inspiration from the great
> > exifprobe program :
> >
> > http://www.virtual-cafe.com/~dhh/tools.d/exifprobe.d/exifprobe.html
> >
> > If we using Exiv2 for 0.9.0, we will using 2 lib about Exif : Exiv2 and
> > libkexif (using libexif). Sure in the future, all code depending of
> > libkexif must be ported to Exiv2, but this can do later 0.9.0...
> >
> > Note : Exiv2 Exif bytes array data is compatible with libkexif. We can
> > extract exif metadata using Exiv2 and displaying that using libkexif
> > without problem...
> >
> > Any suggestions welcome.
> >
> > Gilles Caulier
>
> After I have seen some possible choices, I think that exiv2 is the best one
> at this moments, so I agree with Gilles.
>
> To Gilles: if I get to finish de icc stuf some day I would like to help you
> with metadata code :-/

of course,  no problem. The first is to have all viewpoint about from all...

If you want to study Exif/IPTC/DNG/TIFF-EP/ etc., i recommend to print and 
read these links :

TIFF - TIFF/EP :
ftp://ftp.remotesensing.org/pub/libtiff/TIFF6.pdf
http://www.awaresystems.be/imaging/tiff/tifftags.html

nota last libtiff  support already all TIFF/EP tags.

DNG :
http://www.adobe.com/products/dng/pdfs/dng_spec.pdf

nota libtiff will support all DNG tags normally.

Exif/IPTC :
http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/
http://park2.wakwak.com/~tsuruzoh/Computer/Digicams/exif-e.html
http://www.iptc.org/pages/index.php

Gilles



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