[Digikam-users] editing with Color Management enabled is very slow?

Marcel Wiesweg marcel.wiesweg at gmx.de
Mon Mar 25 18:45:19 GMT 2013

> > There is a configuration switch to use lcms2, I have not yet tested this.
> > Default is lcms1.
> Thanks! Marcel. Is this a compile time switch? I don't see any options
> that mention lcms in the digiKam settings.

Yes, this is a CMake option
OPTION(ENABLE_LCMS2            "Link digiKam to LCMS2 instead LCMS1 
(experimental) (default=OFF)"      OFF)

> 1. Specify a default "system" monitor profile.
> 2. Load the default "system" monitor profile "vcgt" information (if
> there is any) to the video LUTS.
> 3. Assist the user in managing all their monitor, printer, scanner,
> camera, working space, and etc, profiles. "Managing profiles" means
> knowing *which profile*, located *where* on your system, is available
> for *what purpose*. "Managing" doesn't include actually doing any ICC
> profile conversions.
> 4. Assist the user in creating device profiles (colorhug/colord; not
> sure if KDE Desktop color management has anything equivalent).

All these, particularly 3), having reliably implemented on our target systems 
is something I am looking forward to.

> As Remco says, conceptually speaking there is a profound difference
> between an artificial working space profile such as ProPhoto or
> BetaRGB, and a device profile such as a monitor profile or a printer
> profile (device profiles "characterize" whereas working space profiles
> "define how to code the color" as Remco says). But practically
> speaking, whether converting from one working space profile to
> another, or from a working space profile to a device profile, an ICC
> profile conversion is used.

I have developed a (probably simplistic) understanding which leads me when 
coding CM support: 
Whenever I have pixel data, I need a color profile which tells me how to 
interpret the numbers. 
When I have a file in sRGB and the user wants to edit images in AdobeRGB, I 
tell lcms to convert the pixel numbers. When the AdobeRGB pixels from the 
image editor are displayed on the monitor which has a profile, I tell lcms to 
convert the pixel numbers. When the user wants to save the file, I add the 
AdbobeRGB profile to the metadata.

> That is interesting. As you say, it appears that digiKam (a KDE/qt
> app) isn't aware that colord assigned a system monitor profile.

At the moment, we only support the ancient XAtom solution. If there is any 
modern solution, via DBus or whatever, we dont read it.


More information about the Digikam-users mailing list