get_kmat.m

采用matlab编写的数字图像恢复程序

  function Kmat = get_Kmat(kernel_hat)
  
%  Kmat = get_Kmat(kernel_hat)
%
%  Construct block Toeplitz matrix Kmat with Toeplitz blocks which 
%  corresponds to 2-d integral operator. 
%
%  kernel_hat contains the 2-D FFT of the discretized kernel of the 
%  operator. This kernel has been zero extended, so its size is 4 times
%  that of Kmat.

  [nx2,ny2] = size(kernel_hat);
  kernel = real(ifft2(kernel_hat));
  nx = nx2 / 2;
  ny = ny2 / 2;
  kernel = kernel(1:nx,1:ny);
  N = nx*ny;
  hx = 1/nx;
  hy = 1/ny;

%  Use MATLAB's Toeplitz function to construct matrix.

  Kmat = zeros(N,N);
  for j = 1:ny
    jmin = (j-1)*nx+1;
    jmax = j*nx;
    for jp = 1:ny
      jpmin = (jp-1)*nx+1;
      jpmax = jp*nx;
      arg = kernel(:,abs(j-jp)+1);
      block = toeplitz(arg);
      Kmat(jmin:jmax,jpmin:jpmax) = block;
    end
  end

  Kmat = Kmat * (hx * hy);