MATLAB: Please check the code of image steganography using LSB technique on egdes. It is giving an error which i am unable to find.

edgeerrorimage processinglsb methodsteganography

a=imread('Lenna.png');
b=rgb2gray(a);
edge_b=edge(b,'sobel');
imshow(edge_b);
   message = 'hello lenna'
      message = strtrim(message);
      m = length(message) * 8;
      AsciiCode = uint8(message); 
      binaryString = transpose(dec2bin(AsciiCode,8));
      bst = binaryString(:);
      N = length(bst);
      z = zeros(N,1); 
      for k = 1:N
          if(bst(k) == '1')
              z(k) = 1;
          else
              z(k) = 0;
          end
      end
height = size(b,1);
      width = size(b,2);
k1=m;
while k1>0,
for i=1:height-1
for j=1:width-1
if edge_b(i,j)==1
    lsb=mod(b(i,j),2);
    if (lsb == z(k1))
        b(i,j) = b(i,j);
    else
         if(lsb == 1)
            b(i,j) = b(i,j) - 1;
         else
            b(i,j) = b(i,j) + 1;
         end
    end
    k1 = k1 - 1;
end
end
end
end
error: ??? Attempted to access z(0); index must be a positive integer or logical.

Best Answer

there is no need for while loop.
for i=1:height-1
for j=1:width-1
if k1>0
if edge_b(i,j)==1
lsb=mod(b(i,j),2);
if (lsb == z(k1))
      b(i,j) = b(i,j);
else
       if(lsb == 1)
          b(i,j) = b(i,j) - 1;
       else
          b(i,j) = b(i,j) + 1;
       end
end
k1 = k1 - 1;
end
end
end
end
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