How can I recover a hidden text in a Picture

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Jadem Molina 2014-11-5

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https://ww2.mathworks.cn/matlabcentral/answers/161439-how-can-i-recover-a-hidden-text-in-a-picture

编辑： Geoff Hayes 2014-11-14

I got this code below to Hide a text in a Picture, but I can not recover the hidden text. Can someone help me please

 c = imread('any_image.jpg');
 message = 'hi this is sagar from nagpur..'
 message = strtrim(message);
 m = length(message) * 8;
 AsciiCode = uint8(message); 
 binaryString = transpose(dec2bin(AsciiCode,8));
 binaryString = binaryString(:);
 N = length(binaryString);
 b = zeros(N,1); %b is a vector of bits
 for k = 1:N
     if(binaryString(k) == '1')
         b(k) = 1;
      else
         b(k) = 0;
      end
 end
 s = c;
 height = size(c,1);
 width = size(c,2);
 k = 1; Array=[];l=1;my=1;
 for i = 1 : height
     for j = 1 : width
         LSB = mod(double(c(i,j)), 2);
         if (k>m || LSB == b(k))
             s(i,j) = c(i,j);
             l=k+1;
         else 
             if(LSB == 1)
                 s(i,j) = c(i,j) - 1;
             else
                 s(i,j) = c(i,j) + 1;
                 Array(my)=l;
                 l=l+1;
                 my= my + 1;
             end
             k = k + 1;
         end
     end
 end
 imwrite(s, 'hiddenmsgimage.bmp');
 k = 1;my=1;ur=1;
 for i = 1 : height
     for j = 1 : width
         if( k<=m )
             if (my<numel(Array) && Array(my)==ur)
                 b(k)=~(mod(double(s(i,j)),2));
         else
             b(k) = mod(double(s(i,j)),2);
         end
         k = k + 1;
         my= my + 1;
     end
     ur=ur+1;
  end
end

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Geoff Hayes 2014-11-6

Jadem - you should first verify that the algorithm to embed the secret text is what you and/or makes sense. It seems that it only embeds one bit of the secret message whenever the bit that you want to add does not match the least significant bit (lsb) of the kth image pixel. And every time a zero lsb is replaced with a one, then the Array is updated. What is the intent behind this array?

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