Wavelet watermark level2
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This document describes a watermarking algorithm that embeds a watermark into an image using discrete wavelet transforms. It performs a 2-level discrete wavelet transform on the image and watermark. It then adds a scaled version of the watermark coefficients to the image coefficients if they exceed a threshold. The inverse discrete wavelet transform is applied to get the watermarked image. It also describes how to detect the watermark by filtering the watermarked image and subtracting the original, then applying wavelet transforms to the difference.
![Watermark algorithm
? function [D]=blockdwt2c(A,W);
?
? [row,col]=size(A);
?
? Tr=250;
? k=0.01;
?
? [ca,ch,cv,cd] = dwt2(A,'Haar');
? c1 = [ch cv cd];
?
? %%%%%%Wavelet level 2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
?
? [ca1, ch1, cv1, cd1]= dwt2(ca,'Haar');
?
? c2=[ch1 cv1 cd1];
?
? [h, w] = size(ca1');
? [m, n] = size(c2');
?
? W=dmgb(W,A);
?
? %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Here we take the wavelet transform of the
? %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%watermark](https://image.slidesharecdn.com/waveletwatermarklevel2-130216142609-phpapp02/85/Wavelet-watermark-level2-2-320.jpg)
![Watermark algorithm
?
?
continued
[caa chh cvv cdd]=dwt2(W,'Haar');
? W=caa;
? size(W);
?
? % Adding watermark image.
?
? for i=1:h
? for j=1:w
? if ca1(i,j)>Tr
? Ca(i,j)=ca1(i,j)+k*W(i,j); % <--------k*abs(double(c1(i,j)))*W(i,j); de olabilir
? else
? Ca(i,j)=ca1(i,j);
? end
? end
? end
?
? % CH1=C1(1:h,1:w);
? % CV1=C1(1:h,w+1:2*w);
? % CD1=C1(1:h,2*w+1:3*w);
?
? D0= double( idwt2(Ca,ch1, cv1, cd1,'Haar') );
?
? D= double(idwt2(D0, ch, cv, cd, 'Haar'));](https://image.slidesharecdn.com/waveletwatermarklevel2-130216142609-phpapp02/85/Wavelet-watermark-level2-3-320.jpg)
![Reversing and detecting
the watermark
? h = fspecial('gaussian');
? >> I2 = imfilter(marked,h);
? imshow(uint8(marked)),
title('Original Image')
? figure, imshow(uint8(I2)),
title('Filtered Image')
? >> a=I2-image1;
? >> [ca ch cv
cd]=dwt2(a,'haar');
? >> [ca1 ch1 cv1 cd1]=
dwt2(ca,'haar');
? >> imshow(ca1)](https://image.slidesharecdn.com/waveletwatermarklevel2-130216142609-phpapp02/85/Wavelet-watermark-level2-4-320.jpg)
Wavelet watermark level2
- 2. Watermark algorithm ? function [D]=blockdwt2c(A,W); ? ? [row,col]=size(A); ? ? Tr=250; ? k=0.01; ? ? [ca,ch,cv,cd] = dwt2(A,'Haar'); ? c1 = [ch cv cd]; ? ? %%%%%%Wavelet level 2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% ? ? [ca1, ch1, cv1, cd1]= dwt2(ca,'Haar'); ? ? c2=[ch1 cv1 cd1]; ? ? [h, w] = size(ca1'); ? [m, n] = size(c2'); ? ? W=dmgb(W,A); ? ? %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Here we take the wavelet transform of the ? %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%watermark
- 3. Watermark algorithm ? ? continued [caa chh cvv cdd]=dwt2(W,'Haar'); ? W=caa; ? size(W); ? ? % Adding watermark image. ? ? for i=1:h ? for j=1:w ? if ca1(i,j)>Tr ? Ca(i,j)=ca1(i,j)+k*W(i,j); % <--------k*abs(double(c1(i,j)))*W(i,j); de olabilir ? else ? Ca(i,j)=ca1(i,j); ? end ? end ? end ? ? % CH1=C1(1:h,1:w); ? % CV1=C1(1:h,w+1:2*w); ? % CD1=C1(1:h,2*w+1:3*w); ? ? D0= double( idwt2(Ca,ch1, cv1, cd1,'Haar') ); ? ? D= double(idwt2(D0, ch, cv, cd, 'Haar'));
- 4. Reversing and detecting the watermark ? h = fspecial('gaussian'); ? >> I2 = imfilter(marked,h); ? imshow(uint8(marked)), title('Original Image') ? figure, imshow(uint8(I2)), title('Filtered Image') ? >> a=I2-image1; ? >> [ca ch cv cd]=dwt2(a,'haar'); ? >> [ca1 ch1 cv1 cd1]= dwt2(ca,'haar'); ? >> imshow(ca1)