[Digikam-devel] JPEG lossless crop

[Sebastian Röder]

> Le Mercredi 4 Janvier 2006 14:28, Mikolaj Machowski a ?crit?:
> > Dnia wtorek, 3 stycznia 2006 20:35, Gilles Caulier napisa?:
> > > > Using another file format is not an option here cause the print
> > > > houses expect jpeg and I don't want it to be to complicated (have to
> > > > explain it to my parents who are not that familar with computers).
> > >
> > > no and no. This task will not be complicated when on the fly image
> > > files conversion will be implemented in camera interface (typically to
> > > convert JPEG to PNG of TIFF) without lost all meta-data, ICC profiles,
> > > embedded thumbs, etc. It's planed to digiKam 0.9.x series...
> >
> > But will be on-the-fly conversion implemented for export?
> >
> > Still there is no good way to export images just to folder external to
> > digiKam collection.
>
> No. The files will be converted on the target album selected for download.

This does not solve my problem cause most online photo services want jpg. I 
would have to convert from tiff/png > jpg at the end of the process, no 
matter how easy it is to convert from jpg > png/tiff on download. And here 
again the whole jpg > png > jpg thing becomes losy.

The idea of automatic conversion on download is great for most image 
manipulation tasks (I'm looking forward to have this feature - honesly I 
didn't know that png is lossless) but not for the one and very common task to 
recieve (jpg) photos from a standard digikam (that means no RAW available) 
crop it to the right ascpect ratio for printing (that is 2:3 aspect ratio) 
and send the jpgs to an online printing service without a quality loss.

The ratio crop in digikam does just that (and does it great) but it is lossy. 
Now I would say OK I have to live with that and it is a jpg limitation but IT 
IS NOT! JPEGTRAN CAN DO THIS JOB LOSSLESS (that means without recoding)!

See this link for details: http://sylvana.net/jpegcrop/

I don't know the internals of the existing ratio crop tool in digikam but my 
question is whether one could a) use jpegtran as "backend" to do the job 
lossless (downside: another dependency - but jpeg tools should be installed 
on every linux distro) or b) adopt some code of the jpegtran lossless crop 
functionality into digikam.

I hope I made things a little more clear now - it's always hard to explain 
such complicated things in a foreign language without beeing misunderstood.