0001 0002 function [mssim, ssim_map] = ssim_index(img1, img2, K, window, L) 0003 0004 if (nargin < 2 | nargin > 5) 0005 ssim_index = -Inf; 0006 ssim_map = -Inf; 0007 return; 0008 end 0009 0010 if (size(img1) ~= size(img2)) 0011 ssim_index = -Inf; 0012 ssim_map = -Inf; 0013 return; 0014 end 0015 0016 [M N] = size(img1); 0017 0018 if (nargin == 2) 0019 if ((M < 11) | (N < 11)) 0020 ssim_index = -Inf; 0021 ssim_map = -Inf; 0022 return 0023 end 0024 window = fspecial('gaussian', 11, 1.5); 0025 K(1) = 0.01; 0026 K(2) = 0.03; 0027 L = 255; 0028 end 0029 0030 if (nargin == 3) 0031 if ((M < 11) | (N < 11)) 0032 ssim_index = -Inf; 0033 ssim_map = -Inf; 0034 return 0035 end 0036 window = fspecial('gaussian', 11, 1.5); 0037 L = 255; 0038 if (length(K) == 2) 0039 if (K(1) < 0 | K(2) < 0) 0040 ssim_index = -Inf; 0041 ssim_map = -Inf; 0042 return; 0043 end 0044 else 0045 ssim_index = -Inf; 0046 ssim_map = -Inf; 0047 return; 0048 end 0049 end 0050 0051 if (nargin == 4) 0052 [H W] = size(window); 0053 if ((H*W) < 4 | (H > M) | (W > N)) 0054 ssim_index = -Inf; 0055 ssim_map = -Inf; 0056 return 0057 end 0058 L = 255; 0059 if (length(K) == 2) 0060 if (K(1) < 0 | K(2) < 0) 0061 ssim_index = -Inf; 0062 ssim_map = -Inf; 0063 return; 0064 end 0065 else 0066 ssim_index = -Inf; 0067 ssim_map = -Inf; 0068 return; 0069 end 0070 end 0071 0072 if (nargin == 5) 0073 [H W] = size(window); 0074 if ((H*W) < 4 | (H > M) | (W > N)) 0075 ssim_index = -Inf; 0076 ssim_map = -Inf; 0077 return 0078 end 0079 if (length(K) == 2) 0080 if (K(1) < 0 | K(2) < 0) 0081 ssim_index = -Inf; 0082 ssim_map = -Inf; 0083 return; 0084 end 0085 else 0086 ssim_index = -Inf; 0087 ssim_map = -Inf; 0088 return; 0089 end 0090 end 0091 0092 C1 = (K(1)*L)^2; 0093 C2 = (K(2)*L)^2; 0094 window = window/sum(sum(window)); 0095 img1 = double(img1); 0096 img2 = double(img2); 0097 0098 mu1 = filter2(window, img1, 'valid'); 0099 mu2 = filter2(window, img2, 'valid'); 0100 mu1_sq = mu1.*mu1; 0101 mu2_sq = mu2.*mu2; 0102 mu1_mu2 = mu1.*mu2; 0103 sigma1_sq = filter2(window, img1.*img1, 'valid') - mu1_sq; 0104 sigma2_sq = filter2(window, img2.*img2, 'valid') - mu2_sq; 0105 sigma12 = filter2(window, img1.*img2, 'valid') - mu1_mu2; 0106 0107 if (C1 > 0 & C2 > 0) 0108 ssim_map = ((2*mu1_mu2 + C1).*(2*sigma12 + C2))./((mu1_sq + mu2_sq + C1).*(sigma1_sq + sigma2_sq + C2)); 0109 else 0110 numerator1 = 2*mu1_mu2 + C1; 0111 numerator2 = 2*sigma12 + C2; 0112 denominator1 = mu1_sq + mu2_sq + C1; 0113 denominator2 = sigma1_sq + sigma2_sq + C2; 0114 ssim_map = ones(size(mu1)); 0115 index = (denominator1.*denominator2 > 0); 0116 ssim_map(index) = (numerator1(index).*numerator2(index))./(denominator1(index).*denominator2(index)); 0117 index = (denominator1 ~= 0) & (denominator2 == 0); 0118 ssim_map(index) = numerator1(index)./denominator1(index); 0119 end 0120 0121 mssim = mean2(ssim_map); 0122 0123 return