function?[mssim?ssim_map]?=?ssim（img1?img2?K?window?L）
clc;

%?========================================================================
%?SSIM?Index?with?automatic?downsampling?Version?1.0
%?Copyright（c）?2009?Zhou?Wang
%?All?Rights?Reserved.
%
%?----------------------------------------------------------------------
%?Permission?to?use?copy?or?modify?this?software?and?its?documentation
%?for?educational?and?research?purposes?only?and?without?fee?is?hereby
%?granted?provided?that?this?copyright?notice?and?the?original?authors‘
%?names?appear?on?all?copies?and?supporting?documentation.?This?program
%?shall?not?be?used?rewritten?or?adapted?as?the?basis?of?a?commercial
%?software?or?hardware?product?without?first?obtaining?permission?of?the
%?authors.?The?authors?make?no?representations?about?the?suitability?of
%?this?software?for?any?purpose.?It?is?provided?“as?is“?without?express
%?or?implied?warranty.
%----------------------------------------------------------------------
%
%?This?is?an?implementation?of?the?algorithm?for?calculating?the
%?Structural?SIMilarity?（SSIM）?index?between?two?images
%
%?Please?refer?to?the?following?paper?and?the?website?with?suggested?usage
%
%?Z.?Wang?A.?C.?Bovik?H.?R.?Sheikh?and?E.?P.?Simoncelli?“Image
%?quality?assessment:?From?error?visibility?to?structural?similarity“
%?IEEE?Transactios?on?Image?Processing?vol.?13?no.?4?pp.?600-612
%?Apr.?2004.
%
%?http://www.ece.uwaterloo.ca/~z70wang/research/ssim/
%
%?Note:?This?program?is?different?from?ssim_index.m?where?no?automatic
%?downsampling?is?performed.?（downsampling?was?done?in?the?above?paper
%?and?was?described?as?suggested?usage?in?the?above?website.）
%
%?Kindly?report?any?suggestions?or?corrections?to?zhouwang@ieee.org
%
%----------------------------------------------------------------------
%
%Input?:?（1）?img1:?the?first?image?being?compared
%????????（2）?img2:?the?second?image?being?compared
%????????（3）?K:?constants?in?the?SSIM?index?formula?（see?the?above
%????????????reference）.?defualt?value:?K?=?[0.01?0.03]
%????????（4）?window:?local?window?for?statistics?（see?the?above
%????????????reference）.?default?widnow?is?Gaussian?given?by
%????????????window?=?fspecial（‘gaussian‘?11?1.5）;
%????????（5）?L:?dynamic?range?of?the?images.?default:?L?=?255
%
%Output:?（1）?mssim:?the?mean?SSIM?index?value?between?2?images.
%????????????If?one?of?the?images?being?compared?is?regarded?as?
%????????????perfect?quality?then?mssim?can?be?considered?as?the
%????????????quality?measure?of?the?other?image.
%????????????If?img1?=?img2?then?mssim?=?1.
%????????（2）?ssim_map:?the?SSIM?index?map?of?the?test?image.?The?map
%????????????has?a?smaller?size?than?the?input?images.?The?actual?size
%????????????depends?on?the?window?size?and?the?downsampling?factor.
%
%Basic?Usage:
%???Given?2?test?images?img1?and?img2?whose?dynamic?range?is?0-255
%
%???[mssim?ssim_map]?=?ssim（img1?img2）;
%
%Advanced?Usag