Whitepoint Change

whitepoint_change.nkp

set cut_paste_input [stack 0]
version 8.0 v1
CheckerBoard2 {
 inputs 0
 name CheckerBoard
 selected true
 xpos 70
 ypos -81
}
set N1ef0a2e0 [stack 0]
ColorMatrix {
 matrix {
     {0.997789503 -0.00836600843 -0.0602693859}
     {0.000398521213 1.00088304 0.00511657145}
     {0.00256327284 0.015896121 1.12685204}
   }
 name D65_to_D75_no_chromatic_adaptation_ColorMatrix
 selected true
 xpos 180
 ypos -57
}
push $N1ef0a2e0
ColorMatrix {
 matrix {
     {1.04709975 -0.0433274511 -0.00377231627}
     {0.00207089421 0.997845221 8.38902708e-05}
     {0.00301944016 0.0152122186 0.98176834}
   }
 name D65_to_D75_chromatic_adaptation_ColorMatrix
 selected true
 xpos 180
 ypos -33
}
Viewer {
 input_process false
 name Viewer1
 selected true
 xpos 180
 ypos -9
}

whitepoint_change.py

import numpy as np
import colour

D65 = colour.ILLUMINANTS['cie_2_1931']['D65']
D75 = colour.ILLUMINANTS['cie_2_1931']['D75']

# No chromatic adaptation.
cat = colour.chromatic_adaptation_matrix_VonKries(
    colour.xy_to_XYZ(D65),
    colour.xy_to_XYZ(D75),
    'XYZ Scaling')

M = np.dot(colour.sRGB_COLOURSPACE.XYZ_to_RGB_matrix,
           np.dot(cat, colour.sRGB_COLOURSPACE.RGB_to_XYZ_matrix))

print(M)

# [[  9.97789503e-01  -8.36600843e-03  -6.02693859e-02]
#  [  3.98521213e-04   1.00088304e+00   5.11657145e-03]
#  [  2.56327284e-03   1.58961210e-02   1.12685204e+00]]

# Chromatic adaptation.
cat = colour.chromatic_adaptation_matrix_VonKries(
    colour.xy_to_XYZ(D65),
    colour.xy_to_XYZ(D75),
    'CAT02')
    
# [[  1.04709975e+00  -4.33274511e-02  -3.77231627e-03]
#  [  2.07089421e-03   9.97845221e-01   8.38902708e-05]
#  [  3.01944016e-03   1.52122186e-02   9.81768340e-01]]    

M = np.dot(np.linalg.inv(colour.normalised_primary_matrix(
    colour.sRGB_COLOURSPACE.primaries,
    D75)),
           np.dot(cat, colour.sRGB_COLOURSPACE.RGB_to_XYZ_matrix))

print(M)