laplacian.m

来自「3D shape reconstruction matlab code. It 」· M 代码 · 共 59 行

function L = laplacian(A,dir)
% Compute the laplacian of A using either the forward
% difference scheme or the backward difference scheme
%
% Copyright 2006 Paolo Favaro ([e-mail])
% 
% School of Engineering and Physical Sciences
% Heriot-Watt University, Edinburgh, UK
% 
% Last revision: May 2006
%
% This program can be used only for research purposes.
% This program is distributed WITHOUT ANY WARRANTY; 
% without even the implied warranty of MERCHANTABILITY 
% or FITNESS FOR A PARTICULAR PURPOSE.

% padding size
win = 3;
if (size(A,3) >  1)       | ...
   (size(A,2) == 1)       | ...
   (size(A,1) == 1)       | ...
   (size(A,1) <  2*win+1) | ...
   (size(A,2) <  2*win+1)   
    error('function:laplacian:wrongInput',...
         ['Function laplacian can only handle matrices\n'...
          'and they must be at least %ix%i.'],2*win+1,2*win+1);
end
A = squeeze(A);

[M,N] = size(A);

% compute the regularization term
sx = zeros(M,N);
sy = zeros(M,N);
sxx = zeros(M,N);
syy = zeros(M,N);
% alternate the finite difference method
if strcmp(dir,'forward')
    sx(:,2:N) = diff(A,1,2);
    %sx(:,1) = sx(:,2);
    sy(2:M,:) = diff(A,1,1);
    %sy(1,:) = sy(2,:);
    sxx(:,1:N-1) = diff(sx,1,2);
    sxx(:,N) = sxx(:,N-1);
    syy(1:M-1,:) = diff(sy,1,1);
    syy(M,:) = syy(M-1,:);
else
    sx(:,1:N-1) = diff(A,1,2);
    %sx(:,N) = sx(:,N-1);
    sy(1:M-1,:) = diff(A,1,1);
    %sy(M,:) = sy(M-1,:);
    sxx(:,2:N) = diff(sx,1,2);
    sxx(:,1) = sxx(:,2);
    syy(2:M,:) = diff(sy,1,1);
    syy(1,:) = syy(2,:);
end
L = sxx+syy;

return