The color distortion observed in the example of the previous section was caused by the high correlation between the R, G, and B channels in the case of the RGB image. This is another reason, why in many cases, a safer choice of color channel for color image processing tasks is CIE-L*a*b*. Let's try to alter the function written in the previous section, so that it converts the RGB input image to the CIE-L*a*b* color space, apply the chosen enhancement method only in the Lightness channel (so that the colors remain unaffected) and then transform the resulting image back to RGB:
function output = ColorContrastEnhanceLab(input, method)
% Function for color contrast enhancement of input image in L*a*b*
% Inputs:
% input - Input image
% method – Enhancement method selection (0: histeq
% 1: adapthisteq
% 2: imadjust)
% Output:
% output - Output image (enhanced)
cform = makecform('srgb2lab'); % Make the transform structure
img_lab = applycform(input...