求助:关于小波多尺度边缘提取的问题

rebecca1017

clear all;
load wbarb;
I = ind2gray(X,map);imshow(I);
I1 = imadjust(I,stretchlim(I),[0,1]);figure;imshow(I1);
[N,M] = size(I);

h = [0.125,0.375,0.375,0.125];
g = [0.5,-0.5];
delta = [1,0,0];

J = 3;

a(1:N,1:M,1,1:J+1) = 0;
dx(1:N,1:M,1,1:J+1) = 0;
dy(1:N,1:M,1,1:J+1) = 0;
d(1:N,1:M,1,1:J+1) = 0;

a(:,:,1,1) = conv2(h,h,I,'same');
dx(:,:,1,1) = conv2(delta,g,I,'same');
dy(:,:,1,1) = conv2(g,delta,I,'same');

x = dx(:,:,1,1);
y = dy(:,:,1,1);
d(:,:,1,1) = sqrt(x.^2+y.^2);
I1 = imadjust(d(:,:,1,1),stretchlim(d(:,:,1,1)),[0 1]);figure;imshow(I1);

lh = length(h);
lg = length(g);

for j = 1:J+1
  lhj = 2^j*(lh-1)+1;
  lgj = 2^j*(lg-1)+1;
  hj(1:lhj)=0;
  gj(1:lgj)=0;
  for n = 1:lh
    hj(2^j*(n-1)+1)=h(n);
  end

  for n = 1:lg
    gj(2^j*(n-1)+1)=g(n);
  end
  
  a(:,:,1,j+1) = conv2(hj,hj,a(:,:,1,j),'same');
  dx(:,:,1,j+1) = conv2(delta,gj,a(:,:,1,j),'same');
  dy(:,:,1,j+1) = conv2(gj,delta,a(:,:,1,j),'same');

  x = dx(:,:,1,j+1);
  y = dy(:,:,1,j+1);
  dj(:,:,1,j+1) = sqrt(x.^2+y.^2);

  I1 = imadjust(dj(:,:,1,j+1),stretchlim(dj(:,:,1,j+1)),[0 1]);figure;imshow(I1);
end  
各位高手: 麻烦看一下这个程序,最后函数sqrt算出了模值,但我看不懂极大值是怎摸取得．　
谢谢！