extendspeedband.m

这是一个利用水平集方法进行分割的方法

function speed = extendspeedband( speed, front, band )
% EXTENDSPEEDBAND Extends speed to non-front points
%    EXTENDSPEEDBAND( speed, front ) Extends speed function to
%    all pixels in a narrow band around 'front' given by the
%    indices in 'band'. For each band pixel, its speed is
%    the same as the speed of the closest front pixel.

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

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

% for every pixel in the band
for ii = 1 : n_band;

  % grab the coordinates of the band pixel
  i = band( ii, 1 ); j = band( ii, 2 );

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

  % and copy its speed
  speed( i, j ) = speed( closest_pt( 1 ), closest_pt( 2 ) );
end;