嵌入代码：
function [J,index]=NEC_hide(I, W,alpha,N)
[m,n]=size(I);
index=zeros([2 N]);
if(m*n<N)
error('the pic is too little');
end
DCTI=dct2(I);
x=floor((2*N)^(1/2))+1;
i=0;
for f1=1:x
if i<=(N+1)
for f2=1:(x+1-f1)
if i<=(N+1)
index(1,i+1)=f1;
index(2,i+1)=f2;
i=i+1;
else
break;
end
end
else
break;
end
end
%index=FindNLargest(abs(DCTI),N);
for i=1:N-1
DCTI(index(1,i),index(2,i))=DCTI(index(1,i),index(2,i))*(1+alpha*W(i));
end
J=idct2(DCTI);
J=abs(J);
J=uint8(J);
提取代码：
function Wd=NEC_get(I,J,alpha,N,index)
[m,n]=size(I);
[x,y]=size(J);
if((m~=x)|(n~=y))
error('pics are not fit');
end
DCTI=dct2(I);
DCTJ=dct2(J);
%index=FindNLargest(abs(DCTI),N);
for i=1:N
Wd(i)=(DCTJ(index(1,i),index(2,i))/DCTI(index(1,i),index(2,i))-1)/alpha;
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