Contrast enhancement by intensity preservation-based dynamic histogram equalization for electrowetting display

Abstract

Due to the phenomenon of contact angle saturation and charge trapping, contrast of the electrowetting display will be decreased, and the details of the image will be lost. A histogram equalization algorithm is commonly used to improve the image contrast enhancement. Therefore, in order to improve the display quality of the electrowetting display, this article proposes an extension of dynamic histogram equalization (DHE) techniques, called intensity preservation-based dynamic histogram equalization (IPDHE). Initially, the proposed IPDHE technique separates the histogram into four subhistograms based on intensity preservation. Then, the resultant subhistograms are reshaped by the nonzero bins as the amount of emphasis given on total pixels. Mathematically, the intensity preservation measure of each subhistogram stands for the density and boosted level of the subhistogram. Finally, each subhistogram is equalized. Simulation results show that, for the dataset of test images, the proposed algorithm successfully enhances the contrast of images while preserving the maximum average information content (entropy), presents more image details, and applies to the electrowetting display. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.