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-rw-r--r--src/colour.py83
1 files changed, 75 insertions, 8 deletions
diff --git a/src/colour.py b/src/colour.py
index 92210ea..db51bc1 100644
--- a/src/colour.py
+++ b/src/colour.py
@@ -64,6 +64,21 @@ def ciexyz_to_ciexyy(X, Y, Z):
return [x, y, Y]
+def matrix_mul_vector(matrix, vector):
+ '''
+ Multiplies a matrix with a vector
+
+ @param matrix:list<list<int>> The matrix
+ @param vector:list<int> The vector
+ @return :list<int> The resulting vector
+ '''
+ return [[r * v for r, v in zip(row, vector)] for row in matrix]
+
+
+ciexyz_to_linear_matrix = [[ 3.240450, -1.537140, -0.4985320],
+ [-0.969266, 1.876010, 0.0415561],
+ [0.0556434, -0.204026, 1.0572300]]
+
def ciexyz_to_linear(X, Y, Z):
'''
Convert CIE XYZ to [0, 1] linear RGB
@@ -73,12 +88,13 @@ def ciexyz_to_linear(X, Y, Z):
@param Z:float The Z parameter
@return :[float, float, float] The red, green and blue components
'''
- r = 3.24156 * X - 1.53767 * Y - 0.49870 * Z
- g = -0.96920 * X + 1.87589 * Y + 0.04155 * Z
- b = 0.05562 * X - 0.20396 * Y + 1.05686 * Z
- return [r, g, b]
+ return matrix_mul_vector(ciexyz_to_linear_matrix, [X, Y, Z])
+linear_to_ciexyz_matrix = [[0.4124564, 0.3575761, 0.1804375],
+ [0.2126729, 0.7151522, 0.0721750],
+ [0.0193339, 0.1191920, 0.9503041]]
+
def linear_to_ciexyz(r, g, b):
'''
Convert [0, 1] linear RGB to CIE XYZ
@@ -88,10 +104,7 @@ def linear_to_ciexyz(r, g, b):
@param b:float The blue component
@return :[float, float, float] The X, Y and Z parameters
'''
- X = 0.4123160 * r + 0.3576020 * g + 0.1805010 * b
- Y = 0.2126000 * r + 0.7151990 * g + 0.0722016 * b
- Z = 0.0193297 * r + 0.1192040 * g + 0.9506340 * b
- return [X, Y, Z]
+ return matrix_mul_vector(linear_to_ciexyz_matrix, [r, g, b])
def srgb_to_ciexyy(r, g, b):
@@ -125,3 +138,57 @@ def ciexyy_to_srgb(x, y, Y):
rc = linear_to_standard(*rc)
return rc
+
+def ciexyz_to_cielab(x, y, z):
+ '''
+ Convert from CIE XYZ to CIE L*a*b*
+
+ @param x:float The X parameter
+ @param y:float The Y parameter
+ @param z:float The Z parameter
+ @return :[float, float, float] The L*, a* and b* components
+ '''
+ x /= 0.95047
+ z /= 1.08883
+ f = lambda c : c ** 1 / 3 if c > 0.00885642 else (7.78 + 703 / 99900) * c + 0.1379310
+ l = 116 * f(Y) - 16
+ a = 500 * (f(X) - f(Y))
+ b = 200 * (f(Y) - f(Z))
+ return (l, a, b)
+
+
+def cielab_to_xiexyz(l, a, b):
+ '''
+ Convert from CIE L*a*b* to CIE XYZ
+
+ @param l:float The L* parameter
+ @param a:float The a* parameter
+ @param b:float The b* parameter
+ @return :[float, float, float] The X, Y and Z components
+ '''
+ y = (l + 16) / 116
+ x = a / 500 + y
+ z = y - b / 200
+ f = lambda c : c ** 3 if c ** 3 > 0.00885642 else (c - 0.1379310) / (7.78 + 703 / 99900)
+ (x, y, z) = [f(c) for c in (x, y, z)]
+ x *= 0.95047
+ y *= 1.08883
+ return (x, y, z)
+
+
+def delta_e(a, b):
+ '''
+ Convert the distance (∆E*_ab) between two [0, 1] sRGB colours
+
+ @param a:(float, float, float) The first colour
+ @param b:(float, float, float) The second colour
+ @return :float The difference
+ '''
+ a = standard_to_linear(*a)
+ b = standard_to_linear(*b)
+ a = linear_to_ciexyz(*a)
+ b = linear_to_ciexyz(*b)
+ a = ciexyz_to_cielab(*a)
+ b = ciexyz_to_cielab(*b)
+ return sum([(c1 - c2) ** 2 for c1, c2 in zip(a, b)]) ** 0.5
+