[argyllcms] Tuning ACR Calibrator script w/ ColorChecker and illuminant spectrum readings

  • From: Niccolò Belli <darkbasic4@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 09 Nov 2010 01:04:34 +0100

Hi, I'm writing because it's actually quite hard to do it with Argyll
and I have a wishlist for spec2cie.
Tindemans ACR calibrator script
stores the ColorChecker reference values in ProphotoRGB. It stores
values for three illuminants: A, D50, D65.
If you convert spectral readings w/ spec2cie
spec2cie -i illuminant.sp -o 1931_2 -n measurement.ti3 converted.ti3
then you have to do CAT from the source illuminant (illuminant.sp) to
the destination illuminants (A, D50, D65) and also convert the XYZ/Lab
values to ProphotoRGB.
This is a *VERY* long work to do manually with the help of the Bruce
calculator (http://www.brucelindbloom.com/). Also, the Bruce calculator
only supports few illuminants, so you have to implement your own CAT
into an excel sheet if you want to use your custom illuminant.

So I suggest to add two more parameters to spec2cie: --cat and --rgb
The first will do chromatic adaptation transform to the given
illuminant, the second will convert the chromatic adapted values to the
selected profile.

So the command will be:
spec2cie -i myilluminant.sp -o 1931_2 -n --cat [A|D50|D65] --rgb
Prophoto.icm colorchecker.ti3 copypasteme.ti3


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