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

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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')

Accepted Answer

Walter Roberson
Walter Roberson on 27 Feb 2013
Put in a breakpoint and check the value of max_message
  19 Comments

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More Answers (1)

Lester
Lester on 27 Feb 2013
How do you go about embedding the watermark in the color planes? I didn't get you sir
  5 Comments

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