Window effect of evaluation method of the structural similarity

In order to improve evaluation effect of structural similarity index image, the traditional window selection criterion was improved. By contrasting the window evaluation value before and after improvement, the best window for different databases and different types of distortion was obtained. The results show that the traditional single window does not get the best evaluation result, and the widely-used Gaussian weighted window with standard deviation of 1.5 does not better than the ordinary square window. The optimal windows of different types of image distortion are also different. From the experimental results, for luminance window W1, the bigger the window, the better the evaluation result. And for contrast and structure window W2, the evaluation result is best when W2=7. The results play an important role on optimizing the evaluation method of structural similarity index.