faulty profiles in /usr/share/apps/libkdcraw/profiles folder

[Elle Stone]

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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[Gilles Caulier-4]

Hi Elle,

If i remember Francesco Riosa <[hidden email]> 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 <[hidden email]>:

> 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
>
> _______________________________________________
> Digikam-users mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-users
>

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[Peter Albrecht]

Hi Elle,

thanks for the hint, the explaination and the test sample!

Regards,
        Peter

On 20.08.2013 19:09, Elle Stone wrote:
> 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.
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[Elle Stone]

On 8/20/13, Gilles Caulier <[hidden email]> wrote:
>If i remember Francesco Riosa <[hidden email]> has patch icc
>profile in libkdcraw 3 month ago :
Gilles, thanks! I'll send him an email.

>(see http://brucelindbloom.com/ scroll down to the section called "Adapted
Hmm, my perpetual problem with posting URLs - the proper link to the
Lindbloom page on working space information is this:
http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html

On 8/20/13, Peter Albrecht <[hidden email]> wrote:
>thanks for the hint, the explanation and the test sample!
Peter, you are welcome!

Best,
Elle

--
http://ninedegreesbelow.com - articles on open source digital photography
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[Marcel Wiesweg]

> tags. The problem seems to be that showFoto assigns this faulty
> profile:
>
> /usr/share/apps/libkdcraw/profile/adobergb.icm

The problem is that the original AdobeRGB profile's license does not allow us
to distribute it (at the time when I checked it did not).
It is free to download, and if it's installed - for me it usually is by my
distribution - digikam will find it and use it. But we need a backup, and had
this obviously faulty profile. So, a correct  AdobeRGB profile which we are
allowed to ship would be welcome...
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[Elle Stone]

On 8/23/13, Marcel Wiesweg <[hidden email]> wrote:
> The problem is that the original AdobeRGB profile's license does not allow
> us
> to distribute it (at the time when I checked it did not).
> It is free to download, and if it's installed - for me it usually is by my
> distribution - digikam will find it and use it.

Regarding distribution of the official AdobeRGB, Adobe does require a license.

It also isn't clear what Adobe would consider an allowable name for an
"Adobe-like" open source profile: "Companies who are not Adobe
licensees but who claim to have technology that is compatible with
Adobe RGB (1998) ICC profile software may claim, if true, that their
products are "compatible with the Adobe RGB (1998) ICC profile" as
long as nothing in the circumstances would create consumer confusion."
(http://www.adobe.com/digitalimag/pdfs/AdobeRGB1998.pdf; also see
http://www.adobe.com/digitalimag/adobergb.html)

This whole issue of what to call open source versions of popular
copyrighted profiles is vexing. Rawtherapee has resorted to Large,
Medium, and Small for ProPhotoRGB, AdobeRGB, and sRGB!

> But we need a backup, and had this obviously faulty profile.
> So, a correct  AdobeRGB profile which we are
> allowed to ship would be welcome...

The Argyllcms ClayRGB1998.icm profile that you get when you install
Argyllcms is an open source/public domain version of AdobeRGB.

I'm writing up a little stand-alone c program that generates proper
RGB V4 icc working space profiles. The bare-bones program works. The
next step is to add in descriptions and copyright information. I'm
happy to share the code if anyone is interested.


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[Marcel Wiesweg]

When I look carefully, we use the file  
"profiles/compatibleWithAdobeRGB1998.icc" for AdobeRGB, and this file turns
out to be identical to the ClayRGB profile shipped with ArgyllCMS.

To avoid future confusion, I have deleted the three broken profiles from the
repository.

Marcel
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