SSIM算法的实现代码

全参考图像质量评价 The above (ssim_index.m) is a single scale version of the SSIM indexing measure, which is most effective if used at the appropriate scale. The precisely “right” scale depends on both the image resolution and the viewing distance and is usually difficult to be obtained. In practice, we suggest to use the following empirical formula to determine the scale for images viewed from a typical distance (say 3~5 times of the image height or width): 1) Let F = max(1, round(N/256)), where N is the number of pixels in image height (or width); 2) Average local F by F pixels and then downsample the image by a factor of F; and 3) apply the ssim_index.m program. For example, for an 512 by 512 image, F = max(1, round(512/256)) = 2, so the image should be averaged within a 2 by 2 window and downsampled by a factor of 2 before applying ssim_index.m. When the images are in RGB color, an Matlab function “rgb2gray” is used to convert the images to gray scale.