saeed seggighi

Improved image contrast is one of the most important operations used in image processing and visual processing applications. Histogram equalization is one of the most powerful ways to increase the contrast and improve the quality of digital images. However, this method usually causes an excessive increase in contrast and a loss of part of the image details. Many problems have been resolved in the past two decades in order to overcome the many problems of histogram equalization. In this paper, we have reviewed, categorized and compared the methods proposed in the field of histogram equalization for twenty years.