Color-tone similarity on digital images

A color-tone similarity index (CSIM) between two color images is presented and another index, picture similarity index (PSIM), is also given for a comprehensive similarity comparison between color images. CSIM is defined by a statistical analysis of cumulative histograms in a hue-oriented color space. It characterizes the color distributions, while the existing structural similarity index reflects the spatial structure involved with grayscale images. The behaviors of CSIM are checked by the comparisons of color code chips. Experimental results are given. The proposed indexes combined with SSIM are hopeful to provide a tool for color image quality analysis (IQA).