Enhancer-based contrast enhancement technique for non-uniform illumination and low-contrast images

Abstract

Digital imaging is widely applied in medical, surveillance, machine vision, and other fields. Occasionally, limited light sources during image acquisition process cause non-uniform illumination and low contrast images. Non-uniform illumination and low-contrast image are challenges faced by researchers during the image processing stage. In this paper, a new algorithm called Enhancer-based Contrast Enhancement (EBCE) is proposed to enhance non-uniform illumination and low-contrast image to produce uniform illumination and improve the contrast of images. The proposed method initially derives two enhancers, namely, bright enhancer and dark enhancer from a blurred input image. The bright and dark enhancers respectively enhance the bright and dark regions of the given input image. To enhance the contrast of the image, limited histogram equalization is applied to both regions. Finally, an enhancement ratio is proposed to control the enhancement level of the images. Compared with state-of-the-art methods, the proposed EBCE method successfully produces better images. Visually, the EBCE method produces the best images with more uniform illumination and better contrast. The method produces the best EME, entropy, and NIQE values when applied to 450 test images.