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List:       kwin
Subject:    Re: colour managed KWin (fwd)
From:       Kai-Uwe Behrmann <ku.b () gmx ! de>
Date:       2011-03-04 22:02:55
Message-ID: alpine.LNX.2.00.1103042248540.5758 () roma ! rasena
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Sorry for my late replay.

Am 25.02.11, 01:08 +0100 schrieb Kai-Uwe Behrmann:
> Am 25.02.11, 01:02 +0100 schrieb Thomas Lübking:
>> Am 23.02.2011, 01:28 Uhr, schrieb Fredrik Höglund <fredrik@kde.org>:
>
>> @kai-uwe
>> can you provide mode intel on the colorspace transformation theory?

The best techical resource is the ICC spec [1]. It describes the 
n-dimensional tables used and some matrices and curve types.

> Can you repeat this question perhaps in german? I feel lost.
>
>> (there might be math tricks to get certain std. transformations more 
>> efficiently)

The colour conversion resembles the ICC internal 3D lookup tables at a 
reasonable grid resolution. I found a grid size of 64 fine for desktop 
usage. There are some notes around that[2]. The texture is basical a image 
generated by a colour conversion engine representing slices through the 
RGB colour cube.
ATI and Nvidia provide some examples written in shader language on their 
respective pages.

A pure matrix approach has certain limitations. As I mentioned in a 
previous email, it can be useful for pure matrix profiles like generated 
from EDID. But thats not sufficient for typical non linear behaving 
displays. The primary Linux solution for monitor profiling ArgyllCMS and 
its front end dispcalGUI write table based profiles and not matrix 
profiles. The colour management system Oyranos generates matrix based ICC 
profiles only as a fallback.

kind regards
Kai-Uwe Behrmann
-- 
developing for colour management 
www.behrmann.name + www.oyranos.org


[1] http://www.color.org/icc_specs2.xalter
[2] http://oyranos-cms.blogspot.com/2011/01/speeding-up-compicc.html

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