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utils: raspberrypi: ctt: Improved color matrix fitting

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Added code which optimises the color matrices based off
delta E values for the calibration images. Working in LAB
color space.

Signed-off-by: Ben Benson <ben.benson@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
This commit is contained in:
Ben Benson 2023-07-07 04:17:00 +01:00 • committed by Naushir Patuck
parent a2eadc40a7
commit f8dd17a8f4
3 changed files with 300 additions and 38 deletions
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30
utils/raspberrypi/ctt/colors.py Normal file
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# colors.py - Program to convert from RGB to LAB color space
def RGB_to_LAB(RGB): # where RGB is a 1x3 array. e.g RGB = [100, 255, 230]
num = 0
XYZ = [0, 0, 0]
# converted all the three R, G, B to X, Y, Z
X = RGB[0] * 0.4124 + RGB[1] * 0.3576 + RGB[2] * 0.1805
Y = RGB[0] * 0.2126 + RGB[1] * 0.7152 + RGB[2] * 0.0722
Z = RGB[0] * 0.0193 + RGB[1] * 0.1192 + RGB[2] * 0.9505
XYZ[0] = X / 255 * 100
XYZ[1] = Y / 255 * 100 # XYZ Must be in range 0 -> 100, so scale down from 255
XYZ[2] = Z / 255 * 100
XYZ[0] = XYZ[0] / 95.047 # ref_X = 95.047 Observer= 2°, Illuminant= D65
XYZ[1] = XYZ[1] / 100.0 # ref_Y = 100.000
XYZ[2] = XYZ[2] / 108.883 # ref_Z = 108.883
num = 0
for value in XYZ:
if value > 0.008856:
value = value ** (0.3333333333333333)
else:
value = (7.787 * value) + (16 / 116)
XYZ[num] = value
num = num + 1
# L, A, B, values calculated below
L = (116 * XYZ[1]) - 16
a = 500 * (XYZ[0] - XYZ[1])
b = 200 * (XYZ[1] - XYZ[2])
return [L, a, b]