Hi,
That is because the cromatic adaptation to D50 illuminant
some monitor profiles have. For recovering true primaries,
you can use lcms absolute intent, which tries to "undo" the
chromatic adaptation assuming Bradford.
Just create a transform RGB profile -> XYZ using abs.
colorimetric, then feed (255, 0, 0), (0, 255, 0) and (0, 0, 255)
For example:
F:\lcms>icctrans -t3 -i "sRGB Color Space Profile.icm" -o*XYZ
little cms ColorSpace conversion calculator - v1.9
Enter values, 'q' to quit
R (0..255)? 255
G (0..255)? 0
B (0..255)? 0
X=41.2415 Y=21.2616 Z=1.9318
Then, computing chromaticity:
x = X /(X+Y+Z) = 41.2415/(41.2415+21.2616+1.9318) = 0.64004
Hope this helps,
--
Marti Maria
The littlecms project.
www.littlecms.com
----- Original Message -----
From: "Gerard" <[EMAIL PROTECTED]>
To: <lcms-user@lists.sourceforge.net>
Sent: Wednesday, July 13, 2005 3:05 PM
Subject: Re: [Lcms-user] XYZ values of colorants seem different?
The differences that I experienced seem to come from the adaptation from
the ICC D50 illuminant to the sRGB D65 'illuminant'.
Since I am interested in finding the true primaries of display phosphors
in the ICC profile, it seems that these values could be found if it
possible to replace the white point in a profile to D50 and then use the
function cmsTakeColorants. I have tried to add a whitepoint tag, but that
does not seem to work (it probably adds a second white point at the end
and does not replace the white point). Does anyway have an idea of how it
is possible to get the true RGB chromaticity coordinates of an ICC file
(or how to replace a whitepoint tag) in lcms?
Regards,
Gerard
Dear All,
I am puzzled about the chromaticity coordinates of the colorants in
different profiles. For example, on numerous websites the chromaticity
coordinates of the sRGB profile is described as:
x y
Red 0.64 0.33
Green 0.30 0.60
Blue 0.15 0.06
However, if I use the cmsTakeColorants function (but the same result is
obtained with the ICC profile inspector), I get
x y
Red 0.6485 0.3309
Green 0.3212 0.5978
Blue 0.1559 0.0660
Also when I look at other standard profiles I get decrepancies, especially
in the x-coordinate of Green. Does anyone know why this is? Does it have
to do with the white point or the iluminant data???
Kind regards,
Gerard
-------------------------------------------------------
SF.Net email is sponsored by: Discover Easy Linux Migration Strategies
from IBM. Find simple to follow Roadmaps, straightforward articles,
informative Webcasts and more! Get everything you need to get up to
speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click
_______________________________________________
Lcms-user mailing list
Lcms-user@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/lcms-user
--
No virus found in this incoming message.
Checked by AVG Anti-Virus.
Version: 7.0.323 / Virus Database: 267.8.16/50 - Release Date: 15/07/2005
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.323 / Virus Database: 267.8.16/50 - Release Date: 15/07/2005
-------------------------------------------------------
SF.Net email is sponsored by: Discover Easy Linux Migration Strategies
from IBM. Find simple to follow Roadmaps, straightforward articles,
informative Webcasts and more! Get everything you need to get up to
speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click
_______________________________________________
Lcms-user mailing list
Lcms-user@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/lcms-user
