www.pudn.com > snake.rar > snakeinterp1.m

function [xi,yi] = snakeinterp1(x,y,RES) 
% SNAKEINTERP1  Interpolate the snake to have equal distance RES 
%     [xi,yi] = snakeinterp(x,y,RES) 
% 
%     RES: resolution desired 
 
%     update on snakeinterp after finding a bug 
 
%      Chenyang Xu and Jerry L. Prince, 3/8/96, 6/17/97 
%      Copyright (c) 1996-97 by Chenyang Xu and Jerry L. Prince 
%      Image Analysis and Communications Lab, Johns Hopkins University 
 
% convert to column vector 
x = x(:); y = y(:); 
 
N = length(x);   
 
% make it a circular list since we are dealing with closed contour 
x = [x;x(1)]; 
y = [y;y(1)]; 
 
dx = x([2:N+1])- x(1:N); 
dy = y([2:N+1])- y(1:N); 
d = sqrt(dx.*dx+dy.*dy);  % compute the distance from previous node for point 2:N+1 
 
d = [0;d];   % point 1 to point 1 is 0  
 
% now compute the arc length of all the points to point 1 
% we use matrix multiply to achieve summing  
M = length(d); 
d = (d'*uppertri(M,M))'; 
 
% now ready to reparametrize the closed curve in terms of arc length 
maxd = d(M); 
 
if (maxd/RES<3) 
   error('RES too big compare to the length of original curve'); 
end 
 
di = 0:RES:maxd; 
 
xi = interp1(d,x,di); 
yi = interp1(d,y,di); 
 
N = length(xi); 
 
if (maxd - di(length(di))