Watermarking using DCT: For embedding an image into another image and extracting the same.

I am getting following error while executing my code.

Error:

Index exceeds matrix dimensions.

Error in sheza (line 42)

        dct_block=dct2(cover_object(y:y+blocksize-1,x:x+blocksize-1));

My code is:

clc;
clear all;

start_time=cputime;

k=50;
blocksize=8;

file_name='leena.jpg';

% cover_object=double(rgb2gray(imread(file_name)));

cover_image = imread(file_name);
cover_object = double(cover_image(:,:,1));  %red plane

Mc=size(cover_object,1);       
Nc=size(cover_object,2);          

max_message=Mc*Nc/(blocksize^2);

file_name='football.jpg';
message=double(rgb2gray(imread(file_name)));
Mm=size(message,1);      
Nm=size(message,2);            
len=length(message);
message=round(reshape(message,Mm*Nm,1)./256);

if (len > 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);

watermarked_red = cast(watermarked_image, class(cover_image));
watermarked_image = cat(3, watermarked_red, cover_image(:,:,[2 3]));

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')

Kindly help to get out of this or plz provide me some code for watermarking using DCT for embedding an image into another image.

[Peter Eze]

Please provide the dimensions of your test cover image. Is it a square image and multiple of 8 (your block size)?

[mustafa khalil]

Please provide the code for the return process?

[DGM]

An account that was used once and has since been inactive for 8 years isn't going to come back to life and give you a complete working solution.

I'm pretty sure there are examples on the File Exchange, if there aren't on the forum.