dwt dct steganography code problem

i have problem with my image steganography using dwt and dct. i want to embed image using dct in level 2 dwt. but everytime i extract the image, it only shows noise instead proper image. but if i use level 1 dwt, the image will be extracted properly. in this code i'm using dwt2() to decompose image.

does anyone know how to implement level 2 dwt in this code? in this code i'm using dwt2(), which is single level dwt, to create level 2 dwt but it doesn't work.

here is my embedding process code :

    clear;
    clc;
    cover = imread('airport.jpg');

    [a1 h1 v1 d1] = dwt2(cover,'haar');
    [a2 h2 v2 d2] = dwt2(h1,'haar');
    k=50;           % set minimum coeff difference
    blocksize=8;    % set the size of the block in cover to be used for each bit in    watermark

    cover_object=h2;
    %figure,imshow(cover);title('Original');

    % determine size of cover image
    Mc=size(cover_object,1);          %Height
    Nc=size(cover_object,2);
    % determine maximum message size based on cover object, and blocksize
    max_message=Mc*Nc/(blocksize^2);

    % read in the message image
    msg='mri.jpg';
    message=double(imread(msg));
    Mm=size(message,1);                  %Height
    Nm=size(message,2);                  %Width

    % reshape the message to a vector
    message=round(reshape(message,Mm*Nm,1)./256);

    % check that the message isnt too large for cover
    if (length(message) > max_message)
    error('Message too large to fit in Cover Object');
    % display(length(message));
    % display(max_message);
    end

    % pad the message out to the maximum message size with ones
    message_pad=ones(1,max_message);
    message_pad(1:length(message))=message;
    % generate shell of watermarked image
    watermarked_image=cover_object;
    % process the image in blocks
    % encodes such that (5,2) > (4,3) when message(kk)=0
    % and that (5,2) < (4,3) when message(kk)=1
    x=1;
    y=1;

    for (kk = 1:length(message_pad))
    % transform block using DCT
    dct_block=dct2(cover_object(y:y+blocksize-1,x:x+blocksize-1));    
    % if message bit is black, (1,2) > (2,1)
    if (message_pad(kk) == 0)
        % if (1,2) < (1,1) then we need to swap them
        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    
    % if message bit is white, (1,2) < (2,1)
    elseif (message_pad(kk) == 1)        
        % if (1,2) > (2,1) then we need to swap them
        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

    % now we adjust the two values such that their difference >= k
    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(4,3)+(k/2);
            dct_block(4,3)=dct_block(5,2)-(k/2);            
        end
    else  
         if dct_block(4,3) - dct_block(5,2) < k
            dct_block(4,3)=dct_block(5,2)+(k/2);  
            dct_block(5,2)=dct_block(4,3)-(k/2);
        end
    end

    % transform block back into spatial domain
    watermarked_image(y:y+blocksize-1,x:x+blocksize-1)=idct2(dct_block);    

    % move on to next block. At and of row move to next row
    if (x+blocksize) >= Nc
        x=1;
        y=y+blocksize;
    else
        x=x+blocksize;
    end
    end

    % convert to uint8 and write the watermarked image out to a file
    watermarked_image_int=uint8(watermarked_image);
    h2 = watermarked_image;
    y1=idwt2(a2,h2,v2,d2,'haar');
    y2=idwt2(a1,h1,v1,d1,'haar');
    imwrite(uint8(y2),'stegano.jpg','jpg');
    PSNR(cover,y2)
    % display watermarked image
    subplot(2,2,1),imshow(cover);title('Original');
    subplot(2,2,2),imshow(imread(msg));title('Pesan');
    subplot(2,2,3),imshow(y2,[]);title('Stegano Image');

here is my extraction process :

    clear;
    clc;
    cover = imread('stegano.jpg');

    [a1 h1 v1 d1]= dwt2(cover,'haar');
    [a2 h2 v2 d2]= dwt2(h1,'haar');
    start_time=cputime;
    blocksize=8; 

    % determine size of watermarked image
    Mw=size(h2,1);                %Height
    Nw=size(h2,2);                %Width

    % determine maximum message size based on cover object, and blocksize
    max_message=Mw*Nw/(blocksize^2);

    % read in original watermark
    file_name='logo.jpg';
    orig_watermark=double(imread(file_name));

    % determine size of original watermark
    Mo=size(orig_watermark,1);        %Height
    No=size(orig_watermark,2);        %Width

    % process the image in blocks
    x=1;
    y=1;
    for (kk = 1:max_message)

    % transform block using DCT
    dct_block=dct2(h2(y:y+blocksize-1,x:x+blocksize-1));

    % if dct_block(5,2) > dct_block(4,3) then message(kk)=0
    % otherwise message(kk)=1
    if dct_block(5,2) > dct_block(4,3)
        message_vector(kk)=0;
    else
        message_vector(kk)=1;
    end

    % move on to next block. At and of row move to next row
    if (x+blocksize) >= Nw
        x=1;
        y=y+blocksize;
    else
        x=x+blocksize;
    end
    end

    % reshape the embeded message
    message=reshape(message_vector(1:Mo*No),Mo,No);

    % display processing time
    elapsed_time=cputime-start_time,

    % display recovered message
    figure(2)
    imshow(uint8(message),[])
    title('Recovered Message')

[vaishali]

message=round(reshape(message,Mm*Nm,1)./256); is giving error like "To RESHAPE the number of elements must not change.". What is the solution for that?

Answer 1

[Image Analyst]

Try imshow(yourArray, []). Unless you have the [] it's possible the display could look like garbage.

[Maulana Wahid]

   [a1 h1 v1 d1] = dwt2(cover,'haar');
    [a2 h2 v2 d2] = dwt2(h1,'haar');

is this the right method to do 2 level dwt?

[jasmine kaur]

plz provide me code for steganography usoing dwt and then dct

[Image Analyst]

Sorry, I don't have the wavelet toolbox. I was answering only a possible solution to "it only shows noise instead proper image", which can happen if you have a floating point image instead of a uint8 image. I can't help with wavelet problems. It seems like Wayne King is the only one who does that and he hasn't been too active here lately. You might want to call tech support if you have an error or syntax problem, but not with algorithm development questions.

[Animesh Angrish]

Please ignore if already solved

This is not the correct way for a 2nd level DWT

[a1 h1 v1 d1] = dwt2(cover,'haar');
[a2 h2 v2 d2] = dwt2(h1,'haar');

Use instead

[a1 h1 v1 d1] = dwt2(cover,'haar');
[a2 h2 v2 d2] = dwt2(a1,'haar');

Because 2nd level decomposition happens in the approximation coefficient part not horizontal detailing

hope this would help

Answer 2

[Vinod Mangalore]

message=double(imread(msg));

      Mm=size(message,1);   

      Nm=size(message,2);    

message=round(reshape(message,Mm*Nm,1)./256); ERROR- "To RESHAPE the number of elements must not change."

can anyone tell me the solution??

[Walter Roberson]

You are reading in an RGB image. It is not Mm by Nm in size, it is Mn by Nm by 3.

Glancing at your code, it appears to me that you want to do

message = im2bw(message);
message = message(:);

[Vinod Mangalore]

here i'm trying to embed msg image into my cover image, but it says

Error using dwt (line 30)
Message too large to fit in Cover Object. Where am i going wrong?.

output:

max_message =
  937.5000              %cover image

length(newmessage)=906240     %msg image

-------------------------------------------------------------------------------------

msg='C:\Users\User\Desktop\image steganography\i3.jpg';

      message=double(imread(msg));
      Mm=size(message,1);                  %Height
      Nm=size(message,2);                  %Width

      % reshape the message to a vector
      newmessage=round(reshape(message,Mm*Nm*3,1)./256);

      % check that the message isnt too large for cover
      if (length(newmessage) > max_message)
          display(length(newmessage));
          error('Message too large to fit in Cover Object');  %Line 30
      % display(length(message));
      % display(max_message);
      end

[Walter Roberson]

if numel(newmessage) > max_message

But I think you will find that you probably miscalculated max_message.

Your max_message is consistent with you having a cover image of about 75 x 100 pixels, and that you are trying to store an RGB image of about 472 * 640 into the 75 x 100 cover image.

[rafika brahmi]

can someone help me , i run the same code i don't have the same logo in the extraction part please help me

[Image Analyst]

Possibly. Please do something to allow people to help you.