function?[mssim?ssim_map]?=?ssim（img1?img2?K?window?L）
%SSIM?Index?Version?1.0
%Copyright（c）?2003?Zhou?Wang
%All?Rights?Reserved.
%
%The?author?was?with?Howard?Hughes?Medical?Institute?and?Laboratory
%for?Computational?Vision?at?Center?for?Neural?Science?and?Courant
%Institute?of?Mathematical?Sciences?New?York?University?USA.?He?is
%currently?with?Department?of?Electrical?and?Computer?Engineering
%University?of?Waterloo?Canada.
%
%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.?4?Apr.?2004.
%----------------------------------------------------------------------
%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;
%???K?=?[0.01?0.03];
%???window?=?ones（8）;
%???L?=?255;
%???[mssim?ssim_map]?=?ssim_index（img1?img2?K?window?L）;
%
%See?the?results:
%
%???mssim????????????????????????%Gives?the?mssim?value
%???imshow（max（0?ssim_map）.^4）??%Shows?the?SSIM?index?map
%
%========================================================================

if?（nargin??5）????????%參數個數小于2個或者大于5個則退出
???mssim?=?-Inf;
???ssim_map?=?-Inf;
???return;
end
if?（size（img1）?~=?size（img2））???%對比的兩幅圖大小要一致，否則退出
???mssim?=?-Inf;
???ssim_map?=?-Inf;
???return;
end
[M?N]?=?size（img1）;?????????%將圖1的大小賦值給M?N
if?（nargin?==?2）????????????%參數為2時
???if?（（M?????????mssim?=?-Inf;
????????ssim_map?=?-Inf;
????????return
???end
???window?=?fspecial（‘gaussian‘?11?1.5）;?%建立預定義的濾波算子。
???%為高斯低通濾波，有兩個參數，hsize表示模板尺寸，默認值為[3?3]，sigma為濾波器的標準值，單位為像素，默認值為0.5

?屬性????????????大小?????日期????時間???名稱
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?????文件????????6281??2017-10-29?10:56??ssim.m
?????文件?????????520??2017-10-29?10:57??ssimTest.m