restrict_dcoef.m

来自「采用matlab编写的数字图像恢复程序」· M 代码 · 共 40 行

  function [dcoefxh,dcoefyh] = restrict_dcoef(dcoefxh,dcoefyh,nlevels)
  
%  [dcoefxH,dcoefyH] = restrict_dcoef(dcoefxh,dcoefyh,nlevels)
%
%  Restrict diffusion coefficient for CCFD discretization of 
%  the differential operator
%      Lv = -div( dcoef grad u)
%         = -d/dx(dcoef du/dx) - d/dy(dcoef du/dy)
%  to coarse grid. 

  [nm1,n] = size(dcoefxh);
  [tmp1,tmp2] = size(dcoefyh);
  
  if n-1 ~= nm1
    disp(' *** Error in restrict_dcoef.m. Size of dcoefxh is incorrect ***');
    return
  elseif tmp1-1 ~= tmp2
    disp('*** Error in restrict_dcoef.m. Size of dcoefyh is incorrect ***');
    return
  elseif tmp1 ~= n
    disp('*** Error in restrict_dcoef.m. size(dcoefxh) ~= size(dcoefyh`) ***');
    return
  end
  
  if nargin == 2
    nlevels = 1;
  elseif log2(n) < nlevels + 1
    disp(' *** Error in restrict_dcoef.m. Too many restriction levels ***');
    return
  end
  
  for kk = 1:nlevels
    tmp = dcoefxh(2:2:nm1,:);
    dcoefxh = (tmp(:,1:2:nm1) + tmp(:,2:2:n)) / 4;
    tmp = dcoefyh(:,2:2:nm1);
    dcoefyh = (tmp(1:2:nm1,:) + tmp(2:2:n,:)) / 4;
    n = n/2;
    nm1 = n-1;
  end