Approximated unsharp masking on equi-hue plane in RGB color space

Unsharp masking is a common method of image sharpening. If unsharp masking is applied to each RGB component of a color image, the hue of the output image is changed from that of the input image. A hue-preserving unsharp masking method has been proposed thus far. However, the effect of image sharpening is slightly small. In this paper, we propose a new hue-preserving unsharp masking method that sharpens the image effectively. In the proposed method, componentwise unsharp masking is approximated by linear transformation satisfying Naik’s hue-preserving condition, and the gamut problem is solved by processing in an equi-hue plane in an RGB color space. In the experiments, the effectiveness of the proposed method is verified by qualitative and quantitative evaluations.