MATLAB: This is a dct code on watermark embedding. Please fix it

dctImage Processing Toolboxwatermarking

The error I'm encountering is this –>
Warning: Size vector should be a row vector with integer elements.
> In watermarkemb at 27
??? Index exceeds matrix dimensions.
Error in ==> watermarkemb at 36
    dct_block=dct2(cover_object(x:x+blocksize-1,y:y+blocksize-1));
This is the code –>
clc;
clear all;
start_time=cputime;
k=50;
blocksize=8;
file_name='scene.jpg';
cover_object=double(rgb2gray(imread(file_name)));
Mc=size(cover_object,1);       
Nc=size(cover_object,2);          
max_message=Mc*Nc/(blocksize^2);
file_name='fishy.jpg';
message=double(rgb2gray(imread(file_name)));
Mm=size(message,1);      
Nm=size(message,2);                  
message=round(reshape(message,Mm*Nm,1)./256);
if (length(message) > max_message)
    error('Message too large to fit in Cover Object')
end
message_pad=ones(1,max_message);
message_pad(1:length(message))=message;
watermarked_image_r=cover_object;
x=1;
y=1;
for (kk = 1:length(message_pad))
      dct_block=dct2(cover_object(y:y+blocksize-1,x:x+blocksize-1));
      if (message_pad(kk) == 0)
          if (dct_block(5,2) < dct_block(4,3))
                  temp=dct_block(4,3);
                  dct_block(4,3)=dct_block(5,2);
                  dct_block(5,2)=temp;
          end
      elseif (message_pad(kk) == 1)
          if (dct_block(5,2) >= dct_block(4,3))
                  temp=dct_block(4,3);
                  dct_block(4,3)=dct_block(5,2);
                  dct_block(5,2)=temp;
          end
      end
      if dct_block(5,2) > dct_block(4,3)
          if dct_block(5,2) - dct_block(4,3) < k
              dct_block(5,2)=dct_block(5,2)+(k/2);
              dct_block(4,3)=dct_block(4,3)-(k/2);            
          end
      else  
           if dct_block(4,3) - dct_block(5,2) < k
              dct_block(4,3)=dct_block(4,3)+(k/2);  
              dct_block(5,2)=dct_block(5,2)-(k/2);
          end
      end
      watermarked_image(y:y+blocksize-1,x:x+blocksize-1)=idct2(dct_block);    
      if (x+blocksize) >= Nc
          x=1;
          y=y+blocksize;
      else
          x=x+blocksize;
      end
  end
watermarked_image_int=uint8(watermarked_image);
imwrite(watermarked_image_int,'dct1_watermarked_circuit.jpg','jpg');
elapsed_time=cputime-start_time,
subplot(211);imshow(cover_object,[]);title('Original Image')
subplot(212);imshow(watermarked_image,[]);title('Watermarked Image')

Best Answer

Put in a breakpoint and check the value of max_message
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