initdist.m

这是一个利用水平集方法进行分割的方法

function newphi = initdist( phi, front )
% INITDIST Reinitialize to signed distance function
%    INITDIST( phi, front ) Reinitializes all points in phi to the
%    signed distance of the point to the front.

% grab the size of phi
[ m, n ] = size( phi );

% grab the total number of front points
n_front = size( front, 1 );

% fill the new phi function with zeros to start
newphi = zeros( size( phi ) );

% if there are no front points then return
if( n_front == 0 )
  return;
end

% for every pixel
for i = 2 : m - 1;
  for j = 2 : n - 1;

    % find the front pixel it is closest to
    closest_dist = inf;
    for k = 1 : n_front;
      dist = sum( ( front( k, : ) - [ i, j ] ).^2 );
      if( dist < closest_dist )
	closest_dist = dist;
      end;
    end;

    % and reinitialize the distance
    newphi( i, j ) = sign( phi( i, j ) ) * ceil( sqrt( closest_dist ) );

  end;
end;