[Digikam-users] Comments in png files

[Gilles Caulier]

2007/11/12, Paweł Marciniak <pave at o2.pl>:
>
> Gilles Caulier wrote:
>
> > 2007/11/5, Paweł Marciniak <pave at o2.pl>:
> >>
> >> Thank you Gilles for replying!
> >>
> >> Gilles Caulier wrote:
> >> > Exiv2 do not support yet PNG metadata for writting. Patch still
> >> uncomplete
> >> > on my computer.
> >> > [...]
> >> > yes, Caption, date, rating, and tags are store in digiKam database.
> >>
> >> I see. Is there a way (it may even involve some hacking) to retrieve
> the
> >> captions from db and embed them in jpeg files? Otherwise it's A LOT of
> >> rewriting for me :(
> >
> >
> > But al is always done by digiKam. Are you sure to have set on right
> right
> > options in Metadata setup dialog page ?
>
> Actually, this is a bug. I filed it already:
> http://bugs.kde.org/show_bug.cgi?id=152208
>
> >>> When converting manually with convert, no error is raised, but when I
> >>> try
> >>
> >> >> to
> >> >> view the converted image in digiKam, no metadata is shown at all.
> >> >
> >> > Exif and iptc ??? Impossible (:=))). All my photo collection are in
> PNG
> >> > (taken originally from JPEG or RAW), and metadata still present of
> >> course.
> >> >
> >> > Witch camera you use ? Can you send me a JPEG file taken with your
> >> camera
> >> > to test. How are you converted your JPEG files to PNG ? Using Camera
> >> > interface during download ?
> >>
> >> Yes, there's nothing after opening the photo in digiKam (display(1),
> >> however, sees exif metadata in the jpeg, but not iptc). I found out
> that
> >> the digiKam console says:
> >>
> >> 8<-------------------------------------
> >> Warning: IPTC dataset Iptc.Application2.Preview has invalid size 67904;
> >> skipped.
> >
> >
> > This is the problem. Preview (an embeded and reduced JPEG image) is set
> by
> > digiKam in IPTC to speed up preview loading (F4).
> >
> > problem is than preview IPTC can be larger than 64Kb (see iptc/iim
> paper)
> > and a jpeg section (used to embeded iptc in jpeg file) is limited to
> 64Kb.
> > Ther eis no size limitattion with PNG (or TIFF)
>
> OK, thanks A LOT for that pointer! It allowed me to find a workaround by
> removing the iptc sections from png files with `convert +profile iptc`,
> and
> then seamlessly (well, not really, see the above bug) finishing the work
> with digiKam.



No.

No need to remove the whole IPTC content. Just remove the
iptc.application2.preview tags. You can use ExifTool to do it over PNG file.
This is what i will do in BatchProcessImages kipi-plugins to fix the
problem.

In fact, to be clear, IPTC spec allow to set a preview image size to 256Kb
max. Of course JPEG section is limited to 64Kb. You understand the problem ?

This is a side effect and incompatibility against 2 separate spec written by
2 organizations without a real dialog : iptc.org and jpeg.org...

Gilles
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