www.pudn.com > snake_program.rar > snakeinit.m

function [x,y] = snakeinit(delta) 
%SNAKEINIT  Manually initialize a 2-D, closed snake  
%   [x,y] = SNAKEINIT(delta) 
% 
%   delta: interpolation step 
 
%   Chenyang Xu and Jerry L. Prince, 4/1/95, 6/17/97 
%   Copyright (c) 1995-97 by Chenyang Xu and Jerry L. Prince 
%   Image Analysis and Communications Lab, Johns Hopkins University 
 
hold on 
 
x = []; 
y = []; 
n =0; 
 
% Loop, picking up the points 
disp('Left mouse button picks points.') 
disp('Right mouse button picks last point.') 
 
but = 1; 
while but == 1 
      [s, t, but] = ginput(1); 
      n = n + 1; 
      x(n,1) = s; 
      y(n,1) = t; 
      plot(x, y, 'r-'); 
end    
 
plot([x;x(1,1)],[y;y(1,1)],'r-'); 
hold off 
 
% sampling and record number to N 
x = [x;x(1,1)]; 
y = [y;y(1,1)]; 
t = 1:n+1; 
ts = [1:delta:n+1]'; 
xi = interp1(t,x,ts); 
yi = interp1(t,y,ts); 
n = length(xi); 
x = xi(1:n-1); 
y = yi(1:n-1);