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

[Marcel Wiesweg]

> > 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.

Marcel