g_p_dec.m

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

%水印图像的G-P分解
function f=G_Pde(G)
M=size(G,1);
 a=0.5;
 w=[1/4-a/2,1/4,a,1/4,1/4-a/2];
GG=zeros(M/2,M/2);
    for i=1:M/2
        for j=1:M/2 
             for m=1:5
                for n=1:5
                    W(m,n)= w(m)*w(n);
                     m1=2*i+m-2;
                     n1=2*j+n-2;
                    if m1>M
                        m1=M;
                    end
                    if  n1>M
                        n1=M;
                    end
                    GG(i,j)=GG(i,j)+ W(m,n)*G(m1,n1);
                end
            end
        end
     end
     f=uint8(GG);