[KPhotoAlbum] Colormanagement in kphotoalbum

[Lars Tore Gustavsen]

On Feb 5, 2008 6:42 PM, Jan Kundrát <jkt at gentoo.org> wrote:

> As far as I know, nobody is working on it. What exactly needs to be done
> on the KPA level? I've always been happy with calibrating my monitor and
> X11 using my eyes, printed reference picture from my local photolab and
> the `xgamma` command, but I'm a programmer, not an artist.
>
> Cheers,
> -jkt
>
Sorry Jan for sending this to you privately and not to the list.
Hopefully it goes to the list now.:

I can not go in detail since I'm not a programmer.
There is something called the "ICC profiles in X specification".
(http://www.oyranos.org/wiki/index.php?title=ICC_Profiles_in_X_Specification_0.2)
It describe an X11 atom set by tools like xicc and dispwin
(http://www.argyllcms.com/doc8/dispwin.html)

When the xicc atom are loaded, programs that support it will pick up
the monitor profile. Sample programs are gimp, photoprint, eog, krita,
and ufraw .  I have no idea how much work it is to implement is, but
the first buggy eye of gnome patch are not very big.
http://burtonini.com/computing/eog-cms-20050616.diff

Kphotalbum needs also a function to read embedded color profiles, or
other profile information from images.  Most images from a digital
camera have no color profile embedded, and I think sometimes this is
specified in the meta data to the image.

The advantage of enabling color management is:
1.Colors are accurate and you can trust on them. What you see is what you get
2.Pictures in other colorspace than sRGB are displayed correct. I mean
an picture in Adobe Rgb now longer looks washed out and desaturated.

A calibrated and profiled monitor are important. With the xgamma you
may be able to calibrate the monitor to some point. But It can be
rather difficult and it is easily done with hardware.. The last step,
profiling or characterizing  is best done with a hardware colorimeter
or spectrometer. And you need the display profile in the conversion
process from imagefile to display.  Today you can pick up colorimeter
with linux support  from around $65 , if you live in US. In my county
they start at around $180 for the same device. :-(

Here is a sample image showing my daughters face on a uncalibrated
laptop, after calibration, and after profiling.
http://mulebakken.net/blog/wp-content/uploads/2008/01/linux-colormanagment.jpg
Today we are on step two calibrated display with kphotalbum, since the
vcgt tag in the icc profile here are loaded to the look up table in
the screen card. It is the last step I really dream about. The photos
are from eye of gnome. The first picture is taken after just open the
image. Second after running "dispwin mymonitor.icc" and open the
image. Third image after step two and "dispwin -S mymonitor.icc" and
open the image.

If anyone are interested in this,  peoples  at the openicc list
(http://lists.freedesktop.org/archives/openicc/) may help with the
real details.

Other sources:
http://www.argyllcms.com/doc8/ArgyllDoc.html  (colormanagment software)
http://www.freelists.org/archives/argyllcms/01-2008/msg00265.html
(long discussion started by me )
http://www.littlecms.com/

Lars Tore Gustavsen