Adaptive histogram equalization using variable regions

Some recently introduced variations of adaptive histogram equalization (AHE) are discussed that reduce the sometimes excessive noise amplification produced by AHE in regions whose pixels show only a small range of grey values. A different approach to this problem is proposed in which each regional histogram that covers only a small range of grey values is replaced by a linear combination with the histograms of neighboring regions. The method is called variable-region adaptive histogram equalization