A Hue-Preserving Contrast Enhancement Method Using Histogram Specification for Each RGB Component

The image enhancement is one of the most important image processing techniques and is used to improve the quality of the image captured in various situations. In this study, we propose a novel hue preserving contrast enhancement method that realizes the chroma adjustment while suppressing over-enhancement. In the proposed method, firstly, the histogram of each RGB component of an original image is smoothed by a Gaussian filter. Then, the histogram specification method is performed using the smoothed histogram of each RGB component to spread the pixel distribution in RGB color space. The obtained RGB values are approximated by a linear equation of the input RGB values in order to satisfy Naik and Murthy’s hue preserving condition. If out-of-gamut values occur after the approximation, they are corrected by rearranging them on the equi-hue plane in the RGB color space. In the experiments, the effectiveness of the proposed method is verified by qualitative and quantitative evaluations.