BRIGHTNESS PRESERVATION IN HISTOGRAM EQUALIZATION BASED CONTRAST ENHANCEMENT TECHNIQUES

Abstract

Histogram equalization (HE) is a simple yet effective image enhancement technique. However, it tends to change the brightness of an image significantly, causing annoying artifacts and unnatural contrast enhancement. Brightness preserving bi-histogram equalization (BBHE) and Dualistic Sub-Image Histogram Equalization (DSIHE) have been proposed to overcome the problem but they still fail under certain condition. This paper proposes a novel extension of BBHE referred to as Minimum Mean Brightness Error Bi-Histogram Equalization (MMBEBHE) whose main objective is to minimize the difference between input and output imageís mean. Simulation results show that MMBEBHE is better than BBHE and DSIHE. Besides, this paper also proposes an efficient, integer-based implementation of MMBEBHE. Nevertheless, MMBEBHE also has its limitation. Hence, this paper further proposes a generalization of BBHE referred to as Recursive Mean-Separate Histogram Equalization (RMSHE). RMSHE is featured with scalable brightness preservation. Simulation results show that RMSHE works more elficiently compared to HE, BBHE, DSIHE and MMBEBHE.