How to get standard results in colour management in Linux

I have recently calibrated and profiled my screen, with a ColorHug device.

I’m using Gnome, and have the profile installed through gcm.

When opening an image in GIMP and DigiKam, the results are quite different.

Both apps have Color Management (CM) turned ON, working colour space sRGB with Perceptual rendering intent and the correct display profile (from system). Examples below showing with and without CM.

Sample of same image with different apps

The source image is sRGB.

  • With CM: digiKam presents smooth shadow tones whereas GIMP has very harsh shadows. GIMP gives smooth shadows if set to relative colourmetric intent.

  • Without CM: digiKam renders the image darker (or possibly with more contrast) than GIMP. (why?)

As I understand, the CM application’s job is to take the image, convert from the image’s own profile (sRGB) to the display’s profile, then pass it to the screen. Possibly there might be another transform ( image file → convert to working profile → convert to display profile → display ) but in this case, I believe the image comes with sRGB and the working spaces are also sRGB.

Let’s say, the purpose of the exercise is to make an sRGB image for use online. Can anyone advise on a way to get standard results?


EDIT: it was suggested that the digiKam and GIMP no-cm images were the same except for the crop. I apologise for sloppy cropping, but this is not the case as can be seen here in this division of one version from another (it would be 100% white if they were the same…)

Image showing differences between gimp and digikam without colour management

Answer

DigiKam and Gimp are applying slightly different algorithms to their rendering of the image. Without testing, it’s impossible to say which one (or both) is in error, but that is certainly the case.

If the contrast levels match when one is set to use Perceptual and the other Relative Colorimetric rendering, then the most likely explanation is that one of them has these programmed backwards under the hood.

Attribution
Source : Link , Question Author : artfulrobot , Answer Author : Alan Gilbertson

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