A Reversible Contrast Enhancement Scheme for Color Images

Recently, reversible contrast enhancement (CE) is achieved so that an original image can be recovered after its contrast has been changed. As most of the reversible CE methods are primarily proposed for gray-level images, directly applying them to color images may cause visual distortions. To cope with this issue, a new reversible CE scheme is proposed based on the HSV (hue, saturation, and value) color model. In particular, hue component is preserved during histogram equalization of value component and a new preprocessing is designed for original RGB (red, green, and blue) images. The experimental results show that exact recovery of all test images can be achieved with the proposed scheme. Moreover, several metrics are adopted to measure CE effects, image quality and color difference, respectively. Compared with separately conducting the CE process on the RGB channels, less color differences and better image quality can be simultaneously obtained with the proposed scheme.