In an assignment A(:) = B, the number of elements in A and B must be the same.

Hi, I am trying to embed grayscale image to color image (DCT watermarking). I get the error message :

    In an assignment  A(:) = B, the number of elements in A and B must be the same.
    Error in watermark>pushbutton3_Callback (line 167)

zz_dct_koeff(L+1:L+n) = V;

this is the code

alpha = 0.2; 
L = 1000; 
n = 1000; 

a=getappdata(0,'host'); 
b=getappdata(0,'watermark');

yCbCr = rgb2ycbcr(a);
Y = double(yCbCr(:,:,1));
[xm,xn] = size(Y);
scan_order = jpeg_scan(xm,xn); %access jpeg_scan function

%grayscale image as watermark
wt = double(b);
[M,N] = size(wt);
W = reshape(wt,1,[M*N]);

%transform Y component of host image to DCT
Y_dct = dct2(Y);

temp = Y_dct(:);
zz_dct_koeff = temp;
zz_dct_koeff(scan_order(:)) = temp;

V = zz_dct_koeff(L+1:L+n);

V = V + alpha*abs(V).*W;  %perform watermark

zz_dct_koeff(L+1:L+n) = V;
temp = zz_dct_koeff(scan_order(:));
Yx_dct = reshape(temp,xm,xn);
Yx = uint8(idct2(Yx_dct));
yCbCr(:,:,1) = Yx;
wtm = ycbcr2rgb(yCbCr);

axes(handles.axes3);
imshow(wtm);

Answer 1

[Torsten]

zz_dct_koeff(L+1:L+n) is a single value whereas V is a vector of length M*N.

Thus the assignment

zz_dct_koeff(L+1:L+n) = V;

can't work.

Best wishes

Torsten.

[Faradisa]

would you please give the correct one, sir?

[Torsten]

You are the only person who understands the code you are using. So it's up to you to correct the error I tried to explain to you.

Best wishes

Torsten.