Illuminant-invariant chromaticity
Define the chromaticity (r, 9) for each normalized
pixel by [7]
r = R/(R+G+B) , g = G/(R+G+B) (4)
and consider the 2-channel chromaticity image as that
N x 2 array formed from the color channels of an N-
pixel image. Swain and Ballard also considered his-
tograms of chromaticity, but with no color-band nor-
malization step - instead, they suggested some un-
resolved form of color cclnstancy preprocessing. Here,
the normalization step essentially accomplishes com-
pensation for changing illumination.
histograms