Matrix Dimensions Must Agree

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Mesita Widia Cahyaning on 15 Sep 2019
Commented: per isakson on 16 Sep 2019
Hello I'm new to mathlab and I'm facing this issue. I'm gonna making image watermarking using dct method and this is my code, hope i can find the solution of this, thankyou beforeee
clc;
clear all
if size(I,3)==3
I=rgb2gray(I);
end
figure,imshow(I), title('CITRA Penampung')
if size(W,3)==3
W=rgb2gray(W);
end
figure,imshow(W), title('CITRA Watermark')
alpha = 0.02;
A = dct2(double(I));
B = dct2(double(W));
C = A + alpha*B;
Iw = round(real(idct2(C)));
IIw = uint8(Iw)
figure,imshow(IIw), title('CITRA Terwatermark')
if size(I,3)==3
I=rgb2gray(I);
end
A=dct2(double(I));
C1=dct2(double(Iw));
B1=(C1-A)./alpha;
W1=uint8(idct2(B1));
figure,imshow(W1), title('CITRA Watermark Hasil Ekstraksi')
%this is the error I get
Matrix dimensions must agree.
Error in dctcoba (line 19)
C = A + alpha*B;

per isakson on 15 Sep 2019
Edited: per isakson on 15 Sep 2019
Is this a copy&paste error?
Replacing the line by
might help.

Mesita Widia Cahyaning on 16 Sep 2019
Oh yes, I think I dont really need to re-read Sunset in line 24, and now I'm deleting it.
Done put a breakpoint and this is the values I get:
I = 300x300x3 uint8
W = 512x512 uint8
Walter Roberson on 16 Sep 2019
per isakson on 16 Sep 2019
The line number and the code of the error message doesn't agree with the code of your question. We are thus running diffent codes.