Image contrast enhancement using normalized histogram equalization

Abstract

This paper proposes a modification of histogram equalization method, which enhances the contrast of the image while preserving its brightness and natural appearance. The proposed method avoids un-even expansion of intensities by allocating full dynamic range to narrow ranged segments produced after segmentation process, and each segment is equalized independently. In order to avoid intensity saturation problem, a normalization of intensities is also suggested. Simulation results show that the proposed method outperforms other contemporary methods both qualitatively and quantitatively. It enhances the contrast of the image and preserves its brightness and natural appearance more precisely. The statistical consistency of results is verified using ANOVA statistical tool.