Efficient contrast enhancement through log-power histogram modification

Abstract

A simple power-logarithm histogram modification operator is proposed to enhance digital image contrast. First, a logarithm operator reduces the effect of spikes and transforms the image histogram into a smoothed one that approximates a uniform histogram while retaining the relative size ordering of the original bins. Then, a power operator transforms this smoothed histogram into one that approximates the original input histogram. Contrast enhancement is then achieved by using the cumulative distribution function of the resulting histogram in a standard lookup table-based histogram equalization procedure. The method is computationally efficient, independent of image content, and (unlike most existing contrast enhancement algorithms) does not suffer from the occurrence of artifacts, overenhancement and unnatural effects in the processed images. Performance comparisons with several state-of-the-art contrast enhancement algorithms show that the proposed method achieves appreciable contrast enhancement under diverse conditions.