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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

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The no-CM images are actually the same. They just appear different because of viewing angle. Your results are unusual. I'd have to guess that the original image's color space isn't sRGB. The RGB profile in GIMP is the profile used if no profile is set. In DigiKam the default setting is to convert all images to your default profile. So double check your profile. –  fie Mar 6 '13 at 21:26
    
I did essentially the same thing and didn't get that result but I was working with your final 4-pane image. But with that all of the panes have the same color profile. I'm still thinking it has to do with one of them converting the color profile and the other keeping the original profile. –  fie Mar 7 '13 at 11:31
    
I think this poor soul would've gotten a better answer on Photo.SE. What's this about too old to migrate? –  plainclothes Aug 8 '13 at 22:13
    
Is "perceptual rendering intent" undoing anything in your workflow to cause your situation? There may be something in your settings that is redundant or self-defeating. I regret that this answer is so general. –  Stan Sep 2 '13 at 19:05
    
The root of the issue may lie in "perceptual rendering" as this can cause problems, especially when it's unclear which color profile it should be rendering to and how. Lots of ambiguity there. –  MikeNGarrett Jan 16 at 21:21

1 Answer 1

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.

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