% SVDwatermark.m    將載體圖像分塊成8*8后,然后SVD 
 
K=8;                                        %k=分塊的大小 
Q=50;                                       %Q=量化系數 
W=imread('Hubeiwuhan.bmp');                 %讀取水印圖像Hubeiwuhan.bmp    64*64像素大小 
Mm=size(W,1);                               %Hubeiwuhan.bmp   64*64像素大小 
Nm=size(W,2); 
 
 
figure(1); 
subplot(321); 
imshow(W); 
title('the orginal watermark'); 
 
I=imread('lena512-gray.bmp'); 
subplot(322); 
imshow(I); 
title('the cover image'); 
 
 
II=I;                   % to save the original image(I) 
 
blockrow=Mm; 
blockcol=Nm; 
 
for i=1:blockrow 
    for j=1:blockcol 
        x=(i-1)*K+1; 
        y=(j-1)*K+1; 
        BLOCK=II(x:x+K-1,y:y+K-1); 
        [U,S,V]=svd(double(BLOCK)); 
 
        bit=W(i,j);                             %get the one bit wateramrk=bit 
        remainder=rem(S(1,1),Q); 
        if (bit==1)                             %embedding bit '1' 
            if (remainder<=Q/4) 
                S(1,1)=S(1,1)-remainder-Q/4; 
            else  
                S(1,1)=S(1,1)-remainder+3*Q/4; 
            end 
        else                                    %embedding bit '0' 
            if (remainder>=3*Q/4) 
                S(1,1)=S(1,1)-remainder+5*Q/4; 
            else 
                S(1,1)=S(1,1)-remainder+Q/4; 
            end 
        end 
 
        BLOCKW=U*S*V';                      %SVD 逆變換還原 
         
        II(x:x+K-1,y:y+K-1)=uint8(round(BLOCKW)); 
         
    end 
end 
 
subplot(324); 
imshow(II); 
title('the watermarked image'); 
 
psnr1=PSNR(I,II)                           
 
A=double(II)-double(I); 
rsm=0; 
for i=1:size(A,1) 
    for j=1:size(A,2) 
        rsm=rsm+A(i,j)*A(i,j); 
    end 
end 
rsm=sqrt(rsm)/(size(A,1)*size(A,2))             % rsm是均方誤差 
 
% to extracting the wateramrk from image(II) 
for i=1:blockrow 
    for j=1:blockcol 
        x=(i-1)*K+1; 
        y=(j-1)*K+1; 
        BLOCK=II(x:x+K-1,y:y+K-1); 
        [U,S,V]=svd(double(BLOCK)); 
         
        remainder=rem(S(1,1),Q); 
        if (remainder>Q/2) 
            EW(i,j)=1; 
        else 
            EW(i,j)=0; 
        end 
    end 
end 
subplot(323); 
imshow(EW); 
title('the extracted wateramrk'); 
 
% the watermarked image is attacked  
imwrite(uint8(II),'attack.jpg','jpeg','Quality',70);           %對圖像進行壓縮,保存為attack.jpg 
II1=imread('attack.jpg'); 
 
%中值濾波 
%II1=medfilt2(II);           %中值濾波 
 
%維納濾波 
%II1=wiener2(II);             %維納濾波 
 
%高斯低通濾波，H為預定義的一個濾波器 
%H=fspecial('gaussian',[3,3],0.5); 
%II1=imfilter(II,H); 
 
%II1=imnoise(uint8(II),'salt & pepper',0.005);        %椒鹽加噪 
%II1=imnoise(uint8(II),'gaussian',0.005);             %高斯加噪 
 
%II1=II; 
%II1(1:200,1:200)=255;                              %左上角剪切100*100    
 
%逆時針旋轉5度,然后順時針旋轉5度,以還原原圖像 
%II1=imrotate(II,10,'bilinear','crop');                  % left rotate  5 angle 
%II1=imrotate(II1,-10,'bilinear','crop'); 
 
%縮放攻擊1/2 
%II1=imresize(II,0.5); 
%II1=imresize(II1,2); 
 
 
subplot(326); 
imshow(II1); 
title('the attacked image'); 
 
for i=1:blockrow 
    for j=1:blockcol 
        x=(i-1)*K+1; 
        y=(j-1)*K+1; 
        BLOCK=II1(x:x+K-1,y:y+K-1); 
        [U,S,V]=svd(double(BLOCK)); 
         
        remainder=rem(S(1,1),Q); 
        if (remainder>Q/2) 
            EW(i,j)=1; 
        else 
            EW(i,j)=0; 
        end 
    end 
end 
subplot(325); 
imshow(EW); 
title('the extracted wateramrk'); 
 
corr2=NC(double(W),double(EW))               %攻擊后提取的水印與原水印的歸一化相關系數值N 
psnr2=PSNR(I,II1)                           %攻擊后嵌入水印后的PSNR