How can i study the symmetry in color with matlab?

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Tomas 2012-11-8

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评论： Image Analyst 2014-11-22

Hello,

how can I decide that an image is symmetric or asymmetric in color after dividing it into two parts vertically (the right part and the left part)? thanks

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Answer 1

Image Analyst 2012-11-8

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You could chop the image in half, call fliplr() to flip one of the halves, then check similarity with SSIM (See wikipedia) or something similar like PSNR.

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Tomas 2012-11-8

在 MATLAB Online 中打开

I used this function of SSIM

function [mssim, ssim_map] = ssim_index(img1, img2, K, window, L)
if (nargin < 2 || nargin > 5)
   ssim_index = -Inf;
   ssim_map = -Inf;
   return;
end
if (size(img1) ~= size(img2))
   ssim_index = -Inf;
   ssim_map = -Inf;
   return;
end
[M N] = size(img1);
if (nargin == 2)
   if ((M < 11) || (N < 11))
     ssim_index = -Inf;
     ssim_map = -Inf;
      return
   end
   %window = fspecial('gaussian', 11, 1.5);  %
  % K(1) = 0.01;                      % default settings
  % K(2) = 0.03;                      %
  % L = 255;                                  %
end
if (nargin == 3)
   if ((M < 11) || (N < 11))
     ssim_index = -Inf;
     ssim_map = -Inf;
      return
   end
   window = fspecial('gaussian', 11, 1.5);
   L = 255;
   if (length(K) == 2)
      if (K(1) < 0 || K(2) < 0)
       ssim_index = -Inf;
       ssim_map = -Inf;
       return;
      end
   else
     ssim_index = -Inf;
     ssim_map = -Inf;
     return;
   end
end
if (nargin == 4)
   [H W] = size(window);
   if ((H*W) < 4 || (H > M) || (W > N))
     ssim_index = -Inf;
     ssim_map = -Inf;
      return
   end
   L = 255;
   if (length(K) == 2)
      if (K(1) < 0 || K(2) < 0)
       ssim_index = -Inf;
       ssim_map = -Inf;
       return;
      end
   else
     ssim_index = -Inf;
     ssim_map = -Inf;
     return;
   end
end
if (nargin == 5)
   [H W] = size(window);
   if ((H*W) < 4 || (H > M) || (W > N))
     ssim_index = -Inf;
     ssim_map = -Inf;
      return
   end
   if (length(K) == 2)
      if (K(1) < 0 || K(2) < 0)
       ssim_index = -Inf;
       ssim_map = -Inf;
       return;
      end
   else
     ssim_index = -Inf;
     ssim_map = -Inf;
     return;
   end
end
C1 = (K(1)*L)^2;
C2 = (K(2)*L)^2;
window = window/sum(sum(window));
img1 = double(img1);
img2 = double(img2);
mu1   = filter2(window, img1, 'valid');
mu2   = filter2(window, img2, 'valid');
mu1_sq = mu1.*mu1;
mu2_sq = mu2.*mu2;
mu1_mu2 = mu1.*mu2;
sigma1_sq = filter2(window, img1.*img1, 'valid') - mu1_sq;
sigma2_sq = filter2(window, img2.*img2, 'valid') - mu2_sq;
sigma12 = filter2(window, img1.*img2, 'valid') - mu1_mu2;
if (C1 > 0 && C2 > 0)
   ssim_map = ((2*mu1_mu2 + C1).*(2*sigma12 + C2))./((mu1_sq + mu2_sq + C1).*(sigma1_sq + sigma2_sq + C2));
else
   numerator1 = 2*mu1_mu2 + C1;
   numerator2 = 2*sigma12 + C2;
  denominator1 = mu1_sq + mu2_sq + C1;
   denominator2 = sigma1_sq + sigma2_sq + C2;
   ssim_map = ones(size(mu1));
   index = (denominator1.*denominator2 > 0);
   ssim_map(index) = (numerator1(index).*numerator2(index))./(denominator1(index).*denominator2(index));
   index = (denominator1 ~= 0) & (denominator2 == 0);
   ssim_map(index) = numerator1(index)./denominator1(index);
end
%figure,imshow(ssim_map);
mssim = mean2(ssim_map);
%figure,imshow(mat2gray(ssim_map))
return

but i get this error

??? Undefined function or method 'conv2' for input arguments of type 'double' and attributes 'full 3d real'.
Error in ==> filter2 at 73
        y = conv2(hcol, hrow, x, shape);
Error in ==> ssim_index at 136
mu1   = filter2(window, img1, 'valid');
Error in ==> ssim at 7
[mssim, ssim_map] = ssim_index(img1, img2, K, window, L)

Pamela 2012-11-15

在 MATLAB Online 中打开

Hello

function [mssim, ssim_map] = ssim_index(img1, img2, K, window, L)
if (nargin < 2 || nargin > 5)
   ssim_index = -Inf;
   ssim_map = -Inf;
   return;
end
if (size(img1) ~= size(img2))
   ssim_index = -Inf;
   ssim_map = -Inf;
   return;
end
[M N] = size(img1);
if (nargin == 2)
   if ((M < 11) || (N < 11))
     ssim_index = -Inf;
     ssim_map = -Inf;
      return
   end
   %window = fspecial('gaussian', 11, 1.5);  %
  % K(1) = 0.01;                      % default settings
  % K(2) = 0.03;                      %
  % L = 255;                                  %
end
if (nargin == 3)
   if ((M < 11) || (N < 11))
     ssim_index = -Inf;
     ssim_map = -Inf;
      return
   end
   window = fspecial('gaussian', 11, 1.5);
   L = 255;
   if (length(K) == 2)
      if (K(1) < 0 || K(2) < 0)
       ssim_index = -Inf;
       ssim_map = -Inf;
       return;
      end
   else
     ssim_index = -Inf;
     ssim_map = -Inf;
     return;
   end
end
if (nargin == 4)
   [H W] = size(window);
   if ((H*W) < 4 || (H > M) || (W > N))
     ssim_index = -Inf;
     ssim_map = -Inf;
      return
   end
   L = 255;
   if (length(K) == 2)
      if (K(1) < 0 || K(2) < 0)
       ssim_index = -Inf;
       ssim_map = -Inf;
       return;
      end
   else
     ssim_index = -Inf;
     ssim_map = -Inf;
     return;
   end
end
if (nargin == 5)
   [H W] = size(window);
   if ((H*W) < 4 || (H > M) || (W > N))
     ssim_index = -Inf;
     ssim_map = -Inf;
      return
   end
   if (length(K) == 2)
      if (K(1) < 0 || K(2) < 0)
       ssim_index = -Inf;
       ssim_map = -Inf;
       return;
      end
   else
     ssim_index = -Inf;
     ssim_map = -Inf;
     return;
   end
end
C1 = (K(1)*L)^2;
C2 = (K(2)*L)^2;
window = window/sum(sum(window));
img1 = double(img1);
img2 = double(img2);
mu1   = filter2(window, img1, 'valid');
mu2   = filter2(window, img2, 'valid');
mu1_sq = mu1.*mu1;
mu2_sq = mu2.*mu2;
mu1_mu2 = mu1.*mu2;
sigma1_sq = filter2(window, img1.*img1, 'valid') - mu1_sq;
sigma2_sq = filter2(window, img2.*img2, 'valid') - mu2_sq;
sigma12 = filter2(window, img1.*img2, 'valid') - mu1_mu2;
if (C1 > 0 && C2 > 0)
   ssim_map = ((2*mu1_mu2 + C1).*(2*sigma12 + C2))./((mu1_sq + mu2_sq + C1).*(sigma1_sq + sigma2_sq + C2));
else
   numerator1 = 2*mu1_mu2 + C1;
   numerator2 = 2*sigma12 + C2;
  denominator1 = mu1_sq + mu2_sq + C1;
   denominator2 = sigma1_sq + sigma2_sq + C2;
   ssim_map = ones(size(mu1));
   index = (denominator1.*denominator2 > 0);
   ssim_map(index) = (numerator1(index).*numerator2(index))./(denominator1(index).*denominator2(index));
   index = (denominator1 ~= 0) & (denominator2 == 0);
   ssim_map(index) = numerator1(index)./denominator1(index);
end
%figure,imshow(ssim_map);
mssim = mean2(ssim_map);
%figure,imshow(mat2gray(ssim_map))
return

This method can help me to measure the asymmetry index of a color region of interest?? knowing that the background is black. I have now two images, after dividing the segmented image, each containing a portion of the region although divided along the major axis. So how can I adapt this method to my need??

thanks

Sidra Naeem 2014-11-22

I haven't ssim() function in MATLAB 2013. Can you tell me some other method to implement this in Matlab

Image Analyst 2014-11-22

I did , sort of - did you see the link I gave you? That will have the best methods by people who have studied it intensively. Maybe my guess of SSIM is not even the best way.

If you still want ssim(), upgrade to the latest version of MATLAB, or program it yourself with information from http://en.wikipedia.org/wiki/Structural_similarity

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