[argyllcms] Re: Making profile of uncalibrated display
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 20 Apr 2012 10:12:59 +1000
Ivan Tsyba wrote:
> .cal file contains 256 rows RGB_I RGB_R RGB_G RGB_B table and .ti3 file
> contains 48 rows RGB_R
> RGB_G RGB_B XYZ_X XYZ_Y XYZ_Z table. How to append that 256 elements on 48
> elements?
> So it maybe little bit more sophisticated that just replacing RGB values from
> cal to ti3 file?
They are not appended, the values are replaced by their looked up values.
So:
for each row of the .ti3 file., ie:
SAMPLE_ID RGB_R RGB_G RGB_B ....
.
17 1.4275 34.039 73.682 ...
for each of R, G & B, ie:
G = 34.039
Normalize G = 34.039/100 = 0.34039
Locate lookup point in .cal file for a G value of 0.34039
by locating the RGB_I value it lies between:
RGB_I RGB_R RGB_G RGB_B
0.33725 0.36240 0.39923 0.35515
0.34118 0.36562 0.40221 0.35843
Linearly interpolate the G value
cal_G = (0.34039 - 0.33725)/(0.34118 - 0.33725) * 0.40221
+ (0.34118 - 0.34039)/(0.34118 - 0.33725) * 0.39923
= 0.40161
[Note (0.34039 - 0.33725)/(0.34118 - 0.33725) =
1.0 - (0.34118 - 0.34039)/(0.34118 - 0.33725)]
De-normalize the calibrated G value
cal_G *= 100.0
Replace the G value with its calibrated value in the .ti3 file:
17 nnnnn 40.161 nnnnn ...
etc.
etc.
Graeme Gill.
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