Image Processing

The L*a*b* color model is based on opposite color theory and reference white point (Wyszecki and Stiles, 1982). It is independent of devices used, and is suitable for applications with natural illumination. L*, a*, b* are nonlinearly related to R, G, B, through the middle terms X, Y, Z(tri-stimulus):

$X=0.4902R+0.3099G+0.1999B\left(8.54\right)$

$Y=0.1770R+0.8123G+0.0107B\left(8.55\right)$

$Z=0.0000R+0.0101G+0.9899B\left(8.56\right)$

L*, a*, b* are then computed by

$L^{\ast }=\{\begin{array}{l}116{\left(Y/Y_0\right)}^{1/3}-16ifY/Y_0>0.008856\\ 903.3{\left(Y/Y_0\right)}^{1/3}ifY/Y_0>0.008856\end{array}\left(8.57\right)$

$a^{\ast }=500\left[f\left(X/X_0\right)-f\left(Y/Y_0\right)\right]\left(8.58\right)$

$b^{\ast }=200\left[f\left(Y/Y_0\right)-f\left(Z/Z_0\right)\right]\left(8.59\right)$

where

$$