grey world normalization

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关于grey world normalization，下面是谷歌结果：

Grey world[edit]

The grey world normalization makes the assumption that changes in the lighting spectrum can be modelled by three constant factors applied to the red, green and blue channels of color.^[6] More specifically, a change in illuminated color can be modelled as a scaling α, β and γ in the R, G and B color channels and as such the grey world algorithm is invariant to illumination color variations. Therefore a constancy solution can be achieved by dividing each color channel by its average value as shown in the following formula:

$\left ( \alpha R, \beta G, \gamma B \right ) \rarr \left ( \frac{\alpha R}{\frac{\alpha}{n} \sum_i R }, \frac{\beta G}{\frac{\beta}{n} \sum_i G }, \frac{\gamma B}{\frac{\gamma}{n} \sum_i B } \right )$

As mentioned above, grey world color normalization is invariant to illuminated color variations α, β and γ, however it has one important problem: it does not account for all variations of illumination intensity and it is not dynamic; when new objects appear in the scene it fails.^[6] To solve this problem there are several variants of the grey world algorithm.^[6] Additionally there is an iterative variation of the grey world normalization, however it was not found to perform significantly better.^[7]

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