66 lines
1.4 KiB
Python
66 lines
1.4 KiB
Python
# L*a*b color space conversion
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# from EDSCII
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import math
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def rgb_to_xyz(r, g, b):
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r /= 255.0
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g /= 255.0
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b /= 255.0
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if r > 0.04045:
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r = ((r + 0.055) / 1.055) ** 2.4
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else:
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r /= 12.92
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if g > 0.04045:
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g = ((g + 0.055) / 1.055) ** 2.4
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else:
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g /= 12.92
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if b > 0.04045:
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b = ((b + 0.055) / 1.055) ** 2.4
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else:
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b /= 12.92
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r *= 100
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g *= 100
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b *= 100
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# observer: 2deg, illuminant: D65
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x = r * 0.4124 + g * 0.3576 + b * 0.1805
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y = r * 0.2126 + g * 0.7152 + b * 0.0722
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z = r * 0.0193 + g * 0.1192 + b * 0.9505
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return x, y, z
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def xyz_to_lab(x, y, z):
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# observer: 2deg, illuminant: D65
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x /= 95.047
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y /= 100.0
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z /= 108.883
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if x > 0.008856:
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x = x ** (1.0 / 3)
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else:
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x = (7.787 * x) + (16.0 / 116)
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if y > 0.008856:
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y = y ** (1.0 / 3)
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else:
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y = (7.787 * y) + (16.0 / 116)
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if z > 0.008856:
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z = z ** (1.0 / 3)
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else:
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z = (7.787 * z) + (16.0 / 116)
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l = (116 * y) - 16
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a = 500 * (x - y)
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b = 200 * (y - z)
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return l, a, b
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def rgb_to_lab(r, g, b):
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x, y, z = rgb_to_xyz(r, g, b)
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return xyz_to_lab(x, y, z)
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def lab_color_diff(l1, a1, b1, l2, a2, b2):
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"quick n' dirty CIE 1976 color delta"
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dl = (l1 - l2) ** 2
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da = (a1 - a2) ** 2
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db = (b1 - b2) ** 2
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return math.sqrt(dl + da + db)
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