Modified histogram equalization with variable enhancement degree for image contrast enhancement

Histogram equalization (HE) is one of the common methods used for improving contrast in digital images. However, this technique will cause an effect on brightness saturation in some almost homogeneous area. In order to avoid the saturation effect, mean preserving bi-histogram equalization (BBHE) method is proposed. In this paper, we propose a novel HE with variable enhancement degree. Moreover the BBHE with variable separation intensity is also proposed. Finally, the proposed two methods are combined. In this method, we can control the enhancement degree by two parameters. We also show the guide to decide the two parameters. Since our method is able to control the enhancement degree and the mean of image is tend to be preserved, all kinds of images are enhanced adequately.