[Kde-imaging] Exif data

[Caulier Gilles]

Le Mardi 26 Septembre 2006 19:47, Neil Winchurst a écrit :
> Caulier Gilles wrote:
> > Le Mardi 26 Septembre 2006 19:02, Neil Winchurst a écrit :
> >> Hi there,
> >>
> >> in a recent email this appeared.
> >>
> >>
> >> Second points, is about metadata an pictures format : not all file
> >> formats support metadata ! Exif (the most important format used in
> >> photography) is supported by TIFF, JPEG, and PNG only, but not by TGA,
> >> BMP, JPEG2000, EXR, GIMP, etc.
> >>
> >> Well when I change my photo files in Digikam from JPG to PNG I lose all
> >> the exif data. If I leave the files as JPG then the exif data is kept.
> >> So why don't my png files keep the data as mentioned above?
> >
> > witch digikam release you use ?
> >
> > Gilles
>
> Version 0.8.0.
>

digiKam 0.8.x use libkexif/libexif to manage metadata. These library are very 
limited (to manage only JPEG files) and are now obsolete.

In current timplementation of digiKam (0.9.0-beta2), we using Exiv2 library 
instead. This one can drive JPEG, TIFF, PNG and RAW files formats to extract 
EXIF, Makernotes, GPS, and IPTC metadata.

Actually, Exiv2 can only write meatadat in JPEG, but for the next release, 
PNG, and TIFF (and certainly RAW files) will be availabale in write access.

I'm sure about that : i'm also a developper from Exiv2 project. I will 
implemente the writting access to PNG files.

In digiKam 0.9.0, if you convert a JPEG file to a PNG file, you will see the 
Exif, Makernote, GPS, and IPTC metadata on the right side bar like you can 
see in these screenshots :

http://digikam3rdparty.free.fr/Screenshots/PNGsupportindigiKam1.png
http://digikam3rdparty.free.fr/Screenshots/PNGsupportindigiKam2.png
http://digikam3rdparty.free.fr/Screenshots/PNGsupportindigiKam3.png
http://digikam3rdparty.free.fr/Screenshots/PNGsupportindigiKam4.png

Also, in digikam camera interface, there is a new option to convert on the fly  
all JPEG image to PNG without lost metadata during downloading.

In fact, PNG support Exif, IPTC, and XMP to store metadata informations like a 
byte array in a text chunk. This way is used by ImageMagick/GraphicsMagick 
and Exiftools programs ! Try these command line for example :

#convert foo.jpg foo.png
#convert foo.png foo2.jpg

If foo.jpg has Exif and iptc metadata, foo2.jpg will has too !

Note : in the future, we have planed to add XMP support into Exiv2 library. 
Like this all major metadata used in photography will be supported in digiKam 
and kipi-plugins.

To resume : if you wantto see you Exif data from png file, try digikam 
0.9.0-beta2 (http://www.digikam.org/?q=download)

Gilles Caulier