levelsetband.m

这是一个利用水平集方法进行分割的方法

function phi = levelsetband( im, center, radius, isinside, d_it, m_it, m_name )
% LEVELSETBAND Segment the image using narrow band algorithm
%    LEVELSETBAND( im, center, radius, isinside, d_it, m_it, m_name )
%    Segment the image im using level sets, given that the
%    zero-level, level-set is a circle with the argument center and
%    radius. The current segmented image is displayed every d_it
%    iterations and written to disk every m_iterations with name
%    m_name*.png.

% constants
delta_t  = 0.001;
ITERATIONS = 250;
BAND_ITERATIONS = 100;
BAND_WIDTH = 2;

% initialize the phi function
phi = initphi( size( im ), center, radius, isinside );

% calculate the stopping function
K_I = edgestop( im, 5, 2 );

% keep track of iterations
iterations = 0;

while( iterations < ITERATIONS )

  % determine the front and narrow band points
  [ x, y ] = find( isfront( phi ) );
  front = [ x, y ];
  [ x, y ] = find( isband( phi, front, BAND_WIDTH ) );
  band = [ x, y ];

  % update the narrow band for BAND_ITERATIONS
  for kk = 1 : BAND_ITERATIONS;

    % display current iteration
    fprintf( 1, '%d\n', iterations );

    % display the segmented image every 'd_it' iterations
    if( mod( iterations, d_it ) == 0 )
      disp( 'Displaying segmented image' );
      segim = createimage( im, phi );
      imshow( segim ); drawnow;
    end;

    % write current segmented image to file every 'm_it'
    % iterations
    if( mod( iterations, m_it ) == 0 )
      disp( 'Saving movie frame to file' );
      segim = createimage( im, phi );
      filename = strcat( m_name, sprintf( '%06d', ( iterations / m_it ) + 1 ), '.png' );
      imwrite( segim, filename );
    end;

    % calculate the speed, extend it, and update phi
    speed = calcspeed( phi, K_I, front );
    speed = extendspeedband( speed, front, band );
    phi = phi - delta_t .* speed;

    % increment number of iterations
    iterations = iterations + 1;
  end;

end