[Digikam-users] faulty profiles in /usr/share/apps/libkdcraw/profiles folder

[Gilles Caulier]

Hi Elle,

If i remember Francesco Riosa <francesco at pnpitalia.it> has patch icc
profile in libkdcraw 3 month ago :

https://projects.kde.org/projects/kde/kdegraphics/libs/libkdcraw/repository/revisions/ca2274e40d065e12123f6d32db3c6fe153e621a2

But that all. You can try to ask him to take a look. He has already
managed some ICC problems around digiKam and ported all code from lcm1
to lcms2.

Best

Gilles Caulier

2013/8/20 Elle Stone <l.elle.stone at gmail.com>:
> Back in January, 2013 I filed a bug report
> (https://bugs.kde.org/show_bug.cgi?id=312551) that Showfoto wasn't
> properly opening camera-generated jpegs that had ColorSpace tags
> instead of an embedded ICC profile, IF the ColorSpace tag indicated
> that the image should be AdobeRGB instead of sRGB (sRGB images open
> properly).
>
> Has anyone else encountered this bug? I think I figured out the
> problem, but it's not in the code that reads the embedded metadata
> tags. The problem seems to be that showFoto assigns this faulty
> profile:
>
> /usr/share/apps/libkdcraw/profile/adobergb.icm
>
> There are six profiles in /usr/share/apps/libkdcraw/profiles:
> adobergb.icm, applergb.icm, prophoto.icm, srgb.icm, srgb-d65.icm, and
> widegamut.icm. All of these profiles are available to be assigned to
> images opened by digiKam and Showfoto. You can also convert an image
> to these profiles, or choose them as your default working space.
>
> The reason I'm posting here as well as the bug report is because on my
> computer (running Gentoo, digiKam/showFoto 3.3 and libkdcraw-4.10.5),
> three of these profiles -  adobergb.icm, applergb.icm, and srgb.icm -
> are faulty because they contain unadapted primaries (see
> http://brucelindbloom.com/, scroll down to the section called "Adapted
> Primaries") and so really shouldn't be used for image editing.
>
> If you **assign** one of these faulty profiles to an image, often the
> fact that there's an issue will be obvious because the image will
> acquire a blue color cast. But if you **convert** an image to one of
> these profiles, the only way you'll know there's a problem is if you
> eyedropper what should be a neutral gray color and find out that the
> RGB values don't match, which can create problems while image editing
> (for example, trying to color balance the image).
>
> I've attached a profileless test jpeg that is solid white (all RGB
> values are 255,255,255). Regardless of what working space profile you
> assign to this test jpeg, it should look solid white. But if you
> assign adobergb.icm, applergb.icm, or srgb.icm from the
> /usr/share/apps/libkdcraw/profile/ folder, the test image will look
> blue-green.
>
> The other three profiles - prophoto.icm, srgb-d65.icm, and
> widegamut.icm - are OK to use. The widegamut profile has a 256-point
> TRC instead of a proper gamma=2.2 TRC, but at least it's useable. It
> would be better to change it to a proper gamma=2.2 TRC.
>
> Elle
>
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