Hi,

I'm not sure this will work, but since the amount of effort to
check it is very small, would be worth to give a try.

I'm assuming your LED has channel independency, which
probably is not. Building a accurate profile for that would need 
CLUT, and this is too complex for what I suppose you want.

So, let's try a matrix-shaper profile. That is, let's try to fool
the monitor profiler telling your LED is a monitor.

First you have to fill following sheet:

--cut -------------------------------

LCMS_MEASUREMENT
ORIGINATOR "Monitor measurement template"
NUMBER_OF_SETS "27"
NUMBER_OF_FIELDS "7"
BEGIN_DATA_FORMAT
SAMPLE_ID RGB_R RGB_G RGB_B XYZ_X XYZ_Y XYZ_Z
END_DATA_FORMAT
BEGIN_DATA
CBL 0 0 255 18.0573 7.22046 95.0775
CGR 0 255 0 35.7513 71.521 11.9141
CRD 255 0 0 41.2415 21.2616 1.93481
DMIN 255 255 255 95.05 100.003 108.929
GS1 250 250 250 90.8661 95.6024 104.132
GS2 238 238 238 81.2683 85.5042 93.1305
GS3 221 221 221 68.7256 72.3083 78.7628
GS4 205 205 205 58.0292 61.0535 66.4978
GS5 190 190 190 48.9441 51.4954 56.0883
GS6 175 175 175 40.7471 42.868 46.6949
GS7 160 160 160 33.4106 35.1532 38.2904
GS8 146 146 146 27.3193 28.7445 31.308
GS9 133 133 133 22.2931 23.4589 25.5463
GS10 119 119 119 17.5354 18.4479 20.0928
GS11 107 107 107 13.974 14.7003 16.0156
GS12 95 95 95 10.8765 11.4441 12.4664
GS13 83 83 83 8.22144 8.64868 9.41772
GS14 72 72 72 6.15845 6.47888 7.05872
GS15 63 63 63 4.72412 4.97131 5.41382
GS16 53 53 53 3.3844 3.55835 3.87573
GS17 44 44 44 2.39258 2.5177 2.74353
GS18 36 36 36 1.67542 1.76392 1.91956
GS19 29 29 29 1.16577 1.22681 1.33667
GS20 21 21 21 0.708008 0.747681 0.811768
GS21 15 15 15 0.454712 0.476074 0.518799
GS22 4 4 4 0.112915 0.119019 0.128174
DMAX 0 0 0 0 0 0
END_DATA
--- cut -----------------------------------------

Replace the XYZ values for the measurements of your LED at every RGB on sheet. 
You have to convert from xyY to XYZ, but this is almost trivial. 
Save as LED_measurement.it8

Then, download this simplified monitor profiler: http://www.littlecms.com/mntprf.exe

And type:

mntprf profile.icc LED_measurement.it8

If all works ok, this program will create a profile for your LED. How good
this profile will be is unclear, but probably will serve as a basis for further
refinement.

Regards,
Marti Maria
The little cms project
http://www.littlecms.com
[EMAIL PROTECTED]




----- Original Message ----- 
From: "Justin Cormack" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, February 09, 2004 6:13 PM
Subject: [Lcms-user] advice wanted



I am a programmer with not much colour management background. Quite
happy to release any code I write if it is of use to anyone else.

I need to calibrate a computer controlled LED light so that people can
specify colours and get something close to what they want (what that is
is slightly unclear as they are basically print based people and really
want to specify Pantone, but sRGB will probably do as a start).

I have a Minolta colour meter that will measure Yxy (and is in theory
scriptable, though I dont yet know how much control you get from the
serial interface), so I should be able to get a mapping from 24 bit RGB
device space to Yxy  (possible complete if I can automate it and leave
it in a dark room for a long time).

How do I then go about converting this to an ICC table that I can use
with lcms? If I cant sample all colour values, how should I choose the
selected points?

Thanks very much for any help

Justin Cormack




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See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
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