Hi Kai-Uwe.
chad applies only to illuminant, so it depends on which kind of
profile. On printer profiles, no chromatic adaptation is assumed.
On Display profiles, lcms uses a sort of linear Bradford (same as
sRGB). Works well on most workspace profiles.
Regards,
--
Marti Maria
The littlecms project.
www.littlecms.com
----- Original Message -----
From: "Kai-Uwe Behrmann" <[EMAIL PROTECTED]>
To: "Marti" <[EMAIL PROTECTED]>
Cc: "Lcms Liste" <lcms-user@lists.sourceforge.net>
Sent: Tuesday, October 11, 2005 6:37 PM
Subject: Re: [Lcms-user] ICC profiles -> primaries
Marti,
thanks for the hint.
An other question comes to my mind:
for the absolute intent you need to guess, when chrm or chad are absent?
Or how does you find out the original primaries, which are lost during the
Wtpt->D50 transformation?
regards
Kai-Uwe Behrmann
+ development for color management
+ imaging / panoramas
+ email: [EMAIL PROTECTED]
+ http://www.behrmann.name
Am 10.10.05, 18:54 +0200 schrieb Marti:
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" <[EMAIL PROTECTED]>
To: "Lcms Liste" <lcms-user@lists.sourceforge.net>
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: [EMAIL PROTECTED]
> + 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: [EMAIL PROTECTED]
> > + http://www.behrmann.name
> >
>
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