Modified histogram equalization 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 or shadow in some almost homogeneous area. In order to avoid these effects, mean preserving bi-histogram equalization (BBHE) method is proposed. In this paper, we propose a novel HE with variable enhancement degree (HEwVED). Moreover the BBHE with variable enhancement degree (BBHEwVED) is also proposed. The enhancement degree of each of these methods is controlled by only one parameter. We also show the guide to decide this parameter. 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.