dct_det.m

一个基于dct变换的数字水印算法的源程序,可供进行数字水印学习和研究的学生及科研工作者学习参考

function QQ=dct_det(attacked,tao)
Q_table=[16 11 10 16 24 40 51 61;
        12 12 14 19 26 58 60 55;
        14 13 16 24 40 57 69 56;
        14 17 22 29 51 87 80 62;
        18 22 37 56 68 109 103 77;
        24 35 55 64 81 104 113 92;
        49 64 78 87 103 121 120 101;
        72 92 95 98 112 100 103 99
        ];

ZT=attacked;
[m n]=size(ZT);
chuangai=zeros(m,n);
quality=50;
%块dct变换
for i=1:(m/8);
    for j=1:(n/8);
        width=(i-1)*8+1;
        height=(j-1)*8+1;
        imdct(width:(width+7),height:(height+7))=dct2(ZT(width:(width+7),height:(height+7)));
    end
end
%开辟要比较的数据空间
Q=zeros(1,m*n/8/8/2*6);
watermark=zeros(1,m*n/8/8*6);
%比较zig-zag前6个对应系数

k=1;
for i=1:(m/8/2);
    for j=1:(n/8);
        width=(i-1)*16+1;
        height=(j-1)*8+1;
        l=(k-1)*6+1;
        if round(imdct(width,height))-round(imdct(width+8,height))<tao
            Q(l)=0;
        else
            Q(l)=1;
        end
        if round(imdct(width+1,height))-round(imdct(width+9,height))<tao
            Q(l+1)=0;
        else
            Q(l+1)=1;
        end
        if round(imdct(width,height+1))-round(imdct(width+8,height+1))<tao
            Q(l+2)=0;
        else
            Q(l+2)=1;
        end
        if round(imdct(width,height+2))-round(imdct(width+8,height+2))<tao
            Q(l+3)=0;
        else
            Q(l+3)=1;
        end
        if round(imdct(width+1,height+1))-round(imdct(width+9,height+1))<tao
            Q(l+4)=0;
        else
            Q(l+4)=1;
        end
        if round(imdct(width+2,height))-round(imdct(width+10,height))<tao
            Q(l+5)=0;
        else
            Q(l+5)=1;   
        end
         k=k+1;
    end
end
% imwrite(uint8(J2),'lena256.jpg','quality',quality);
% yy=imread('lena256.jpg');

em_cof=[1 4;2 3;3 2;4 1;4 2;3 3];
em_cof=[4 4;4 5;5 4;2 6;6 2;3 5];
NN=size(em_cof,1);
    
k=1;
err=0;
for i=1:(m/8/2)
    for j=1:(n/8)
        width=(i-1)*16;
        height=(j-1)*8;
        l=(k-1)*6+1;
     
         for kk=1:3  
         qstep=Q_table(em_cof(kk,1),em_cof(kk,2))+1;
           watermark(l)=mod(round(imdct(width+em_cof(kk,1),height+em_cof(kk,2))/qstep),2);
       if watermark(l)~=Q(l)
           err=err+1;
       chuangai((width+1):(width+16),(height+1):(height+8))=1;                
       end
        l=l+1;
         end
         
       width=(i-1)*16+8;
       height=(j-1)*8;
       for kk=4:NN  
       qstep=Q_table(em_cof(kk,1),em_cof(kk,2))+1;
          watermark(l)=mod(round(imdct(width+em_cof(kk,1),height+em_cof(kk,2))/qstep),2);
       if watermark(l)~=Q(l)
           err=err+1;
       chuangai((width-7):(width+8),(height+1):(height+8))=1;                
       end
             l=l+1;
       
         end
         
         k=k+1;
   end
end

figure(2);
imshow(logical(chuangai));
QQ=Q;
err