Range Limited Bi-Histogram Equalization for image contrast enhancement

Abstract

Histogram equalization is a popular technique for enhancing image contrast. However, it tends to change the brightness of an image and hence, this technique is not very well suited to be implemented in consumer electronics, where preserving the original brightness is essential to avoid annoying artifacts. This paper proposes a novel extension of bi-histogram equalization referred to as Range Limited Bi-Histogram Equalization (RLBHE). First, RLBHE divides the input histogram into two independent sub-histograms by a threshold that minimizes the intra-class variance. This is done in order to effectively separate the objects from the background. Then, range of the equalized image is calculated to yield minimum absolute mean brightness error between the original image and the equalized one. The experimental results show that the proposed method has better performance than the existing methods, and preserve the original brightness quite well, so that it is possible to be utilized in consumer electronic products.