the best Parameter to distinguish two different images

hi. I have a set of images. I want to select the most similar image to an input image. for this,I divide images to 16 section and compare variance of these section. but I don't get good result(I mean ,two different images have same variance!). which parameter is good for this purpose? thank you

Answer 1

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/245327-how-to-get-a-similarity-ratio-of-2-figures

Answer 2

[Image Analyst]

See https://en.wikipedia.org/wiki/Content-based_image_retrieval#Content_comparison_using_image_distance_measures