image watermarking cropping attack

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Mevlut Dogru
Mevlut Dogru on 13 Apr 2016
Commented: shivu P on 8 Sep 2017
I applied one level DWT to host image. Then embedding and extracting processing. I applied cropping attack to watermarked image.
But extracted watermark shows black at bottom of the corner.
Actually extracted watermark corrupted, but it should not be black. What is a problem. Could you help me ?
I=double(imread('lena_gray_512.tif'));
W1=double(imread('cameraman256.gif'));
[cA1,cH1,cV1,cD1] = dwt2(I,'haar');
params=[0.03 0.30 0.01 0.01];
for i=1:256
for j=1:256
IWA(i,j) = cA1(i,j) + params(1) * W1(i,j);
IWH(i,j) = cH1(i,j) + params(2) * W1(i,j);
IWV(i,j) = cV1(i,j) + params(3) * W1(i,j);
IWD(i,j) = cD1(i,j) + params(4) * W1(i,j);
end
end
IW=uint8(idwt2(IWA,IWH,IWV,IWD,'haar'));
[krp,rec]=imcrop(IW,[257 257 255 255]);
krp(M1,N1)=0;
tform = maketform('affine',[1 0 0; 0 1 0; rec(1,1)-1 rec(1,2)-1 1]);
krp1= imtransform(krp,tform,'XData',[1 M1],'YData',[1 N1]);
IWD1=IW-krp1;
IWD1 = double(IWD1);
[cA1_IW,cH1_IW,cV1_IW,cD1_IW] = dwt2(IWD1,'haar');
for i=1:256
for j=1:256
WA1(i,j) = (cA1_IW(i,j) - cA1(i,j)) / params(1);
WH1(i,j) = (cH1_IW(i,j) - cH1(i,j)) / params(2);
WV1(i,j) = (cV1_IW(i,j) - cV1(i,j)) / params(3);
WD1(i,j) = (cD1_IW(i,j) - cD1(i,j)) / params(4);
end
end
figure (4);
subplot(3,2,1); imshow(WA1,[]); title('WA5');
subplot(3,2,2); imshow(WH1,[]); title('WH5');
subplot(3,2,3); imshow(WV1,[]); title('WV5');
subplot(3,2,4); imshow(WD1,[]); title('WD5');
  2 Comments
Afeza Ajirah
Afeza Ajirah on 27 Mar 2017
Hello sir, currently my project may related to your project. I have some issues and if possible i want to ask you some questions. May i have your email address? tq
shivu P
shivu P on 8 Sep 2017
define M1=1 and N1=1

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