meanshift.m

Mean shift sementation. matlab

function y=meanshift(g,y0) ;
% Given a grid structure (generated by meanshiftinit) and a starting point
% y0, return the mean shift limit. Normal kernel is used,
% K(x)=c exp(-1/2 * norm(x ./ h)^2)  
% vector h is the kernel size. 
  
y=double(y0) ;

%i=1 ;
while true,
  % Find participating points
  pts=double(rangesearch(g, [ y - g.hmax ; y + g.hmax ])) ;
  %pts=g.x ;
  n=size(pts,1) ;
  if n==0,
    y=y0 ; break ;
  end ;
  % Their contributions
  gker=exp(-0.5*sum(((pts-repmat(y,n,1))./repmat(g.h,n,1)).^2,2)) ;
  y0=y ; 
  y=(gker' * pts)/sum(gker) ;
  %if g.plot;
  %  plot([y(2) y0(2)],[y(1) y0(1)],'r-') ;
  %end ;
  if norm(y-y0)<1e-3,
    break ;
  end ;
%  i=i+1 ;
end ;
%i