www.pudn.com > DCT_watermark.rar > nc.m, change:2006-05-28,size:653b

%Name:		wei--kai19830426@163.com 
%Course:	Digital Watermarking 
%Project: 	Calculates the NC (Normalized Correlation) 
%function:  of watermark images A and A', both of size MxN 
%%%%%%% NC %%%%%% 
 
function N=nc(mark_get,mark_prime) 
mark_get=double(mark_get); 
mark_prime=double(mark_prime); 
if size(mark_get)~=size(mark_prime) 
    error('Input vectors must  be the same size!') 
else 
    [m,n]=size(mark_get); 
    fenzi=0; 
    fenmu=0; 
    for i=1:m 
        for j=1:n 
            fenzi=fenzi+mark_get(i,j)*mark_prime(i,j); 
            fenmu=fenmu+mark_prime(i,j)*mark_prime(i,j); 
        end 
    end 
N=min(fenzi/fenmu,fenmu/fenzi); 
end