function?[mssim?ssim_map]?=?ssim_index（img1?img2?K?window?L）

%========================================================================
%SSIM?Index?Version?1.0
%Copyright（c）?2003?Zhou?Wang
%All?Rights?Reserved.
%
%The?author?is?with?Howard?Hughes?Medical?Institute?and?Laboratory
%for?Computational?Vision?at?Center?for?Neural?Science?and?Courant
%Institute?of?Mathematical?Sciences?New?York?University.
%
%----------------------------------------------------------------------
%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:
%
%Z.?Wang?A.?C.?Bovik?H.?R.?Sheikh?and?E.?P.?Simoncelli?“Image
%quality?assessment:?From?error?measurement?to?structural?similarity“
%IEEE?Transactios?on?Image?Processing?vol.?13?no.?1?Jan.?2004.
%
%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:
%????????????size（img1）?-?size（window）?+?1.
%
%Default?Usage:
%???Given?2?test?images?img1?and?img2?whose?dynamic?range?is?0-255
%
%???[mssim?ssim_map]?=?ssim_index（img1?img2）;
%
%Advanced?Usage:
%???User?defined?parameters.?For?example
%
%???K?=?[0.05?0.05];
%???window?=?ones（8）;
%???L?=?100;
%???[mssim?ssim_map]?=?ssim_index（img1?i