qual_det1.m

multi_wavelet An Image Digital Watermarking Algorithm Based on Bit-Plane-Decomposition and Multi-

  function  [w1,w2,w3,w4,A]=qual_det1(coef,M,delta)%delta量化步长，M为多分辨水印的尺寸2倍
         N=size(coef,1);
         a=1;b=1;c=1;d=2;K=100;%a,b,c,K是密钥，其中d满足ad-bc=1.
         numda=0.618; %numda黄金分割数0.618
         A=zeros(N,N);
 for i=1:M
     for j=1:M
         x(1)=i;y(1)=j;
           for k=1:K-1
               x(k+1)=mod(a*x(k)+b*y(k),N);%水印的嵌入位置由具有混沌特性的Arnold映射确定
                 y(k+1)=mod(c*x(k)+d*y(k),N);
           end
                   if     x(K)==0
                          x(K)=N;
                   end 
                         if  y(K)==0%在增加水印安全性的同时还解决了水印嵌入位置冲突的问题
                             y(K)=N;
                         end
                             %对嵌入位置的小波系数的量化
                             m=x(K);
                             n=y(K);
                             A(m,n)=1;
                                r=fix(coef(m,n)/delta);  
                         if  mod(r,2)==0 
                                  W(i,j)=((1-sign(coef(m,n)))/2);%uint8
                         else     W(i,j)=((1+sign(coef(m,n)))/2);%uint8
                         end
                           
     end
 end
%  w1=uint8(W(1:M/2,1:M/2));
%  w2=uint8(W(1:M/2,M/2+1:M));
%  w3=uint8(W(M/2+1:M,1:M/2));
%  w4=uint8(W(M/2+1:M,M/2+1:M));
    w1=(W(1:M/2,1:M/2));
 w2=(W(1:M/2,M/2+1:M));
 w3=(W(M/2+1:M,1:M/2));
 w4=(W(M/2+1:M,M/2+1:M));