www.gusucode.com > 自己编写的一个基于matlab的图像压缩程序，有GUI界面，不能程度的压缩效果以及信噪比 > 自己编写的一个基于matlab的图像压缩程序，有GUI界面，不能程度的压缩效果以及信噪比/BP神经网络的图像压缩/wavelets压缩/cascade.m

    function [x1,phi,x2,psi] = cascade(h,g,dx)
% Wavelet cascade algorithm

c = h{1}*2/sum(h{1});
x = 0:dx:length(c) - 1;
x1 = x - h{2};
phi0 = 1 - abs(linspace(-1,1,length(x))).';

ii = []; jj = []; s = [];

for k = 1:length(c)
   xk = 2*x - (k-1);
   i = find(xk >= 0 & xk <= length(c) - 1);
   ii = [ii,i];
   jj = [jj,floor(xk(i)/dx)+1];
   s = [s,c(k)+zeros(size(i))];
end

% Construct a sparse linear operator that iterates the dilation equation
Dilation = sparse(ii,jj,s,length(x),length(x));

for N = 1:30
   phi = Dilation*phi0;
   if norm(phi - phi0,inf) < 1e-5, break; end
   phi0 = phi;
end

if norm(phi) == 0
   phi = ones(size(phi))*sqrt(2);   % Special case for Haar scaling function
else
   phi = phi/(norm(phi)*sqrt(dx));  % Rescale result
end

if nargout > 2
   phi2 = phi(1:2:end);  % phi2 is approximately phi(2x)

   if length(c) == 2
      L = length(phi2);
   else
      L = ceil(0.5/dx);
   end

   % Construct psi from translates of phi2
   c = g{1};
   psi = zeros(length(phi2)+L*(length(c)-1),1);
   x2 = (0:length(psi)-1)*dx - g{2} - 0*h{2}/2;

   for k = 1:length(c)
      i = (1:length(phi2)) + L*(k-1);
      psi(i) = psi(i) + c(k)*phi2;
   end
end
return;