RGB-----------Lab

(各分量数值范围：R/G/B: 0~255; L: 0~100, a/b:0~255)

RGB---Lab:

X = 0.412453*R + 0.357580*G + 0.180423*B;

Y = 0.212671*R + 0.715160*G + 0.072169*B;

Z = 0.019334*R + 0.119193*G + 0.950227*B;

X = X/(255*0.950456);

Y = Y/255;

Z = Z/(255*1.088754);

如果Y > 0.008856，则 :

fY = Y^(1/3);

fX = X^(1/3);

fZ = Z^(1/3);

L= 116*fY - 16;

如果Y < 0.008856，则 fY = 7.787*Y + 16/116;

fX = 7.787*X + 16/116;

fZ = 7.787*Z + 16/116;

L= 903.3*Y;

a = 500.0*(fX - fY) +128;

b = 200.0*(fY - fZ) +128;

Lab---RGB:

a = a-128;

b = b-128;

fY = ((L + 16) / 116))^3;

如果fY < 0.008856，则fY = L / 903.3;

Y = fY;

如果fY > 0.008856，则fY = fY^(1/3);

如果fY < 0.008856，则fY = 7.787 * fY + 16/116;

fX = a / 500 + fY;

如果fX > 0.206893，则X = fX^(1/3);

如果fX < 0.206893，则X = (fX - 16/116) / 7.787;

fZ = fY - b /200;

如果fZ > 0.206893，则Z = fZ^(1/3);

如果fX < 0.206893，则Z = (fZ - 16/116) / 7.787;

X = X * 0.950456 * 255;

Y = Y *255;

Z = Z * 1.088754 * 255;

R = 3.240479*X - 1.537150*Y - 0.498535*Z ;

G =-0.969256*X + 1.875992*Y + 0.041556*Z;

B = 0.055648*X - 0.204043*Y + 1.057311*Z;

RGB空间与LAB空间互换