Re: [Lcms-user] ICC profiles -> primaries

[Marti <ma...@li...>]

Kai-Uwe,

Just take the ICC profile as a black-box. The fact some profiles
are implemented as matrix-shaper should be irrelevant.

If you understand primaries as the chromaticity of colorants,
obtaining the primaries should be as easy as using an absolute colorimetric
transform from the given profile to XYZ space, and then obtaining 
the XYZ value of each colorant.  This will work on all colorspaces,
not only on RGB.

Regards,
--
Marti Maria
The littlecms project.
www.littlecms.com





----- Original Message ----- 
From: "Kai-Uwe Behrmann" <ku...@gm...>
To: "Lcms Liste" <lcm...@li...>
Sent: Thursday, October 06, 2005 8:01 PM
Subject: Re: [Lcms-user] ICC profiles -> primaries


> Hi,
> 
> even in danger to repeat this toppic, here comes my own take:
> 
> The primaries stored in the rXYZ,gXYZ and bXYZ tags are part of the
> RGB<->XYZ conversion matrix. They are related to D50. 
> The whitepoint in wtpt represents the original whitepoint of the media. 
> 
> To convert from D50 primaries to oroginal wtpt primaries the chad tag was 
> introduced. It holdes the conversion matrix to come from D50 primaries to 
> wtpt primaries.
> 
> Additional the chromaticity (chrm) tag, natively being in wtpt, can be 
> used to hold the origin in the profile.
> 
> Without knowing the chromaticities (chrm) or the transform (chad)
> conversion is guessing of the right transform. Bradford is a good 
> candidate.
> 
> The good news, now I understand it, the chrm tag is included by lcms 
> during RGB matrix profile generation. Thanks!
> 
> regards
> Kai-Uwe Behrmann
>                                + development for color management 
>                                + imaging / panoramas
>                                + email: ku...@gm...
>                                + http://www.behrmann.name
> 
> 
> Am 03.10.05, 12:38 +0200 schrieb Kai-Uwe Behrmann:
> 
>> Hi,
>> 
>> is there a example to get the real xy primaries from an given matrix 
>> profile, including white point adaption?
>> 
>> regards
>> Kai-Uwe Behrmann
>>                                 + development for color management 
>>                                 + imaging / panoramas
>>                                 + email: ku...@gm...
>>                                 + http://www.behrmann.name
>> 
> 
> 
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