Gray World
The gray world algorithm assumes that given an image of sufficiently varied colors, the average surface color in a
scene is gray.1 This means that the shift from gray of the measured averages on the three channels corresponds to
the color of the illuminant. Three scaling coefficients, one for each color channel, are therefore set to compensate
this shift.
   White Point
Assuming that there is always some white in the scene, the white point algorithm looks for it in the image; its
chromaticity will then be the chromaticity of the illuminant. The white point algorithm determines this white as
the maximum R, maximum G and maximum B found in the image.2, 3 The scaling coefficients are now obtained
by comparing these maxima with the values of the white of the reference illuminant.