[Digikam-devel] [Bug 172196] Color managed view is inaccurate

Milan Knizek knizek at volny.cz
Sat Dec 26 16:19:44 GMT 2009


https://bugs.kde.org/show_bug.cgi?id=172196





--- Comment #26 from Milan Knizek <knizek volny cz>  2009-12-26 17:19:40 ---
(In reply to comment #20)
> I dont know if assigning any CMYK ICC profile and later converting to sRGB
> would improve the general case of any given CMYK image here.

I have done more testing with GIMP, CinePaint, EoG, Krita (and digiKam).
Basically, all of them display the CMYK image w/o any ICC profile differently.

CinePaint: somehow selects a default CMYK ICC profile (even that not set in
settings). I guess it is related to Oyranos project, which was implemented for
CinePaint as a show case (even that I have it switched off). Of course, the
user can assign a different profile in the editor.

Krita: automatically assigns a CMYK ICC profile (internal). The user can assign
another profile manually in the editor.

GIMP: automatically converts the image from CMYK to RGB using the default CMYK
profile from the Settings. If none chosen, it probably does something similar
to the current digiKam's implementation. (Yet, the displayed images are
different.)

Out of these, GIMP converts the image to RGB, while CinePaint and Krita
continue to work with the image in CMYK.

I have not found any information on APP14, whether there is an assumed CMYK /
Offset standard or not. I assume not and that the ICC profile should be ideally
embedded.

For digiKam, I would propose similar behaviour like in GIMP:

If the CMYK image has an embedded profile, it should be used (for thumbnail,
preview and editor).

If the CMYK image does not have embedded profile, digiKam should use the
default one from Settings (does not exist yet...).

Further, in case digiKam editor being set to ask when there is a mismatch
between the embedded and working profiles, the user should have a chance to
select CMYK profiles from drop-down list. (Now CMYK profiles are not listed.)

If the user does not set a default CMYK profile or does not use colour
management, then the current method of simple CMY -> (s)RGB conversion could be
used.

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