由于工作要求，需要把rgb顏色轉成Lab顏色空間。網上一搜一大把的代碼，但是和PS一對比，基本上都不對。

下面這張圖是OpenCV官方文檔的計算方法。

?用Python實現代碼如下：

from math import powparam_13 = 1.0 / 3.0 param_16116 = 16.0 / 116.0Xn = 0.950456 Yn = 1.0 Zn = 1.088754def RGB2XYZ(r, g, b):x = 0.412453 * r + 0.357580 * g + 0.180423 * by = 0.212671 * r + 0.715160 * g + 0.072169 * bz = 0.019334 * r + 0.119193 * g + 0.950227 * breturn x, y, zdef XYZ2Lab(x, y, z):x /= 255 * Xny /= 255 * Ynz /= 255 * Znif y > 0.008856:fy = pow(y, param_13)l = 116.0 * fy - 16.0else:fy = 7.787 * y + param_16116l = 903.3 * fyif l < 0:l = 0.0if x>0.008856:fx = pow(x,param_13)else:fx = 7.787 * x + param_16116if z>0.008856:fz = pow(z,param_13)else:fz = 7.787 * z + param_16116a = 500.0*(fx-fy)b = 200.0*(fy-fz)return [round(l,2), round(a,2), round(b,2)]def RGB2Lab(r, g, b):x, y, z = RGB2XYZ(r, g, b)return XYZ2Lab(x, y, z)if __name__ == '__main__':rgb = [134, 156, 106]print("Lab: " + str(rgb))lab = RGB2Lab(rgb[0], rgb[1], rgb[2])print("Lab: " + str(lab))

下面測試一下運行結果：

rgb: [255, 0, 0] Lab: [53.24, 80.09, 67.2]

rgb: [134, 156, 106] Lab: [80.7, -10.37, 14.71]

rgb: [110, 99, 165] Lab: [70.6, 11.6, -20.76]

?從對比可以看出當rbg為(255,0,0)時和PS的著色器對比基本差不多，但是后面兩個就差得多了。

于是乎經過一番操作，終于實現了和PS結果一樣的算法，代碼如下：

def rgb2lab(rgb):r = rgb[0] / 255.0 # rgb range: 0 ~ 1g = rgb[1] / 255.0b = rgb[2] / 255.0# gamma 2.2if r > 0.04045:r = pow((r + 0.055) / 1.055, 2.4)else:r = r / 12.92if g > 0.04045:g = pow((g + 0.055) / 1.055, 2.4)else:g = g / 12.92if b > 0.04045:b = pow((b + 0.055) / 1.055, 2.4)else:b = b / 12.92# sRGBX = r * 0.436052025 + g * 0.385081593 + b * 0.143087414Y = r * 0.222491598 + g * 0.716886060 + b * 0.060621486Z = r * 0.013929122 + g * 0.097097002 + b * 0.714185470# XYZ range: 0~100X = X * 100.000Y = Y * 100.000Z = Z * 100.000# Reference White Pointref_X = 96.4221ref_Y = 100.000ref_Z = 82.5211X = X / ref_XY = Y / ref_YZ = Z / ref_Z# Labif X > 0.008856:X = pow(X, 1 / 3.000)else:X = (7.787 * X) + (16 / 116.000)if Y > 0.008856:Y = pow(Y, 1 / 3.000)else:Y = (7.787 * Y) + (16 / 116.000)if Z > 0.008856:Z = pow(Z, 1 / 3.000)else:Z = (7.787 * Z) + (16 / 116.000)Lab_L = round((116.000 * Y) - 16.000, 2)Lab_a = round(500.000 * (X - Y), 2)Lab_b = round(200.000 * (Y - Z), 2)return Lab_L, Lab_a, Lab_b

對比一下結果：

rgb: [255, 0, 0] Lab: (54.29, 80.81, 69.89)

rgb: [134, 156, 106] Lab: (61.66, -14.83, 23.57)

rgb: [110, 99, 165] Lab: (45.21, 16.45, -34.45)

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從結果可以看出和PS的結果基本一致。

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總結

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