[Digikam-users] Can't specify input colour profile

[Remco Viëtor]

On Saturday 30 August 2014 13:04:11 Victor Engmark wrote:
> I've enabled colour management and set the working colour space and
> monitor profile. Both of those lists show a whole bunch of profiles,
> from /usr/share/color/icc and ~/.local/share/icc according to the
> "default locations" pop-up. But all input profile selection lists
> ("Camera and Scanner", "Printing and Proofing", image editor pop-up
> for uncalibrated images) are empty.
> 
> I also tried putting AdobeRGB1998.icc into ~/.color/icc. It was
> detected but only listed in the output profile selection lists.
> 
> digiKam output in case it's relevant (removed repeated lines):
> 
> $ digikam
> Object::connect: No such signal 
org::freedesktop::UPower::DeviceAdded(QString)
> Object::connect: No such signal 
org::freedesktop::UPower::DeviceRemoved(QString)
> QSqlDatabasePrivate::removeDatabase: connection 'ConnectionTest' is
> still in use, all queries will cease to work.
> digikam(6346)/digikam (core): Do not use transformForDisplay for
> uncalibrated data but let the RAW loader do the conversion to sRGB
> digikam(6346)/digikam (core): No input profile: invalid Behavior flags 
2097152
> digikam(6346)/digikam (core): Do not use transformForDisplay for
> uncalibrated data but let the RAW loader do the conversion to sRGB
> libpng warning: iCCP: known incorrect sRGB profile
> 
That would be because the AdobeRGB1998.icc profile is a colour space, not 
an input profile. 

The difference is that a colour space describes what RGB value corresponds 
to a real world colour under a given light source, assuming ideal 
behaviour. As real equipment never shows ideal behaviour, we use input and 
output profiles to describe where and how the equipment differs from the 
ideal case. This means that each input and output profile is specific for 
one device, and one device only (for printers, changing paper, ink, or 
print settings can make the profile invalid).

To confuse the issue, both colur spaces and in/output profiles are stored 
in files with a .icc extension...

So, colour space files can be distributed and used by every one, 
independent of the equipment used.

For the input and output profiles you'd have to find one corresponding to 
your equipment (camera, scanner, screen) (or, better but taking some time 
or money) create your own. 

That is also what Digikam tries to tell you (in a rather crytic way)

But, unless you are doing very colour critical work (publicity, scientific 
perhaps), you can get away with leaving the input profiles blank.

Calibrating and profiling your monitor and printer is much more important 
for most of us: 
- the monitor so that others have a fighting chance to see the image as you 
intend it to be seen, 
- the printer so that the final print corresponds as much as possible to 
what your calibrated/profiled screen shows (it will never be exact, due to 
the different principles involved: additive RGB  vs. subtractive CMYK).


Regards, 

Remco

P.S. The libpng warning is a known one btw, try using one of the other 
versions easily available until the warning disappears.