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cielab.py
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# formulas for this file from:
# http://www.easyrgb.com/index.php?X=MATH
import numpy as np
import contextlib
import math
# Converts sRGB color to CIE's XYZ.
# defaults to white, in order to quickly assert white point in CIE-L*a*b*.
def rgb2xyz(rgb = [255, 255, 255]):
# normalize gamut
rgb = np.array(rgb) / 255
xyz = np.zeros(3)
# offset calc.
# linear div. for very small color values.
for i, c in enumerate(rgb):
if c > 0.04045:
rgb[i] = ((c + 0.055) / 1.055)**2.4
else:
rgb[i] = c / 12.92
rgb = np.array(rgb) * 100
# resultin XYZ color coords.
# observer: 2°, illuminant: D65
xyz[0] = rgb[0] * 0.4124 + rgb[1] * 0.3576 + rgb[2] * 0.1805
xyz[1] = rgb[0] * 0.2126 + rgb[1] * 0.7152 + rgb[2] * 0.0722
xyz[2] = rgb[0] * 0.0193 + rgb[1] * 0.1192 + rgb[2] * 0.9505
return xyz
# TODO implement
def xyz2rgb(xyz = rgb2xyz()):
return false
# convert CIE's XYZ to L*a*b*.
# defaults to white.
def xyz2lab(xyz = rgb2xyz()):
lab = np.zeros(3)
# observer = 2°, illuminant = D65
xyz[0] = xyz[0] / 95.047
xyz[1] = xyz[1] / 100.000
xyz[2] = xyz[2] / 108.883
# offset calc.
# linear div. for very small color values.
for i, c in enumerate(xyz):
if c > 0.008856:
xyz[i] = c**(1/3) # third root
else:
xyz[i] = (c * 7.787) + (16/116)
lab[0] = (116 * xyz[1]) - 16
lab[1] = 500 * (xyz[0] - xyz[1])
lab[2] = 200 * (xyz[1] - xyz[2])
return lab
# TODO implement
def lab2xyz(lab = rgb2lab()):
return false
def rgb2lab(rgb = [255, 255, 255]):
return xyz2lab(rgb2xyz(rgb))
def lab2rgb(lab = rgb2lab()):
return xyz2rgb(lab2xyz(lab))
if __name__ == "__main__":
print("white 0xFFFFFF")
print(np.vectorize("%.3f".__mod__)(rgb2xyz()))
print(np.vectorize("%.3f".__mod__)(rgb2lab()))
print("red 0xFF000")
print(np.vectorize("%.3f".__mod__)(rgb2xyz([255, 0, 0])))
print(np.vectorize("%.3f".__mod__)(rgb2lab([255, 0, 0])))
print("green 0x00FF00")
print(np.vectorize("%.3f".__mod__)(rgb2xyz([0, 255, 0])))
print(np.vectorize("%.3f".__mod__)(rgb2lab([0, 255, 0])))
print("blue 0x0000FF")
print(np.vectorize("%.3f".__mod__)(rgb2xyz([0, 0, 255])))
print(np.vectorize("%.3f".__mod__)(rgb2lab([0, 0, 255])))
print("yellow 0xFFFF00")
print(np.vectorize("%.3f".__mod__)(rgb2xyz([255, 255, 0])))
print(np.vectorize("%.3f".__mod__)(rgb2lab([255, 255, 0])))
print("magenta 0xFF00FF")
print(np.vectorize("%.3f".__mod__)(rgb2xyz([255, 0, 255])))
print(np.vectorize("%.3f".__mod__)(rgb2lab([255, 0, 255])))
print("cyan 0x00FFFF")
print(np.vectorize("%.3f".__mod__)(rgb2xyz([0, 255, 255])))
print(np.vectorize("%.3f".__mod__)(rgb2lab([0, 255, 255])))
print("black 0x000000")
print(np.vectorize("%.3f".__mod__)(rgb2xyz([0, 0, 0])))
print(np.vectorize("%.3f".__mod__)(rgb2lab([0, 0, 0])))