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	Mathematik-Online-Aufgabensammlung: Lösung zu
	Aufgabe 1635: Programm zur interaktiven Eingabe einer Bezier-Kurve

function c = bez_draw(window) 

% BEZ_DRAW : draw Bezier polygon
% c = bez_draw(window) 
% interactive input of control points c(k,:)
% with left mouse button (quit with other key)
% in window = [xmin xmax ymin ymax]

if (~exist('window','var') | isempty(window))
  window=[0 1 0 1];
end

hold on;
axis(window); axis square;
t = linspace(0,1);
c = [];

% add control points and draw Bezier curve
while 1 
   [x, y, button] = ginput(1); 
   if button == 1 
      c = [c; x,y];
      cla;
      p = bez_val(c,t); 
      plot(p(:,1),p(:,2),c(:,1),c(:,2),'bo-'); 
   else
      return
   end;
end;


function p = bez_val(c,t) 

% BEZ_VAL : evaluation of Bezier curves
% p = bez_val(c,t) 
% points p(j,:) on a Bezier curve 
% with control points c(k,:) at t(j)

n=size(c,1)-1;
b = zeros(length(t),2*n+1); 
b(:,n+1) = 1;

for k=1:n
   tk = repmat(t(:),1,2*n+1-k);
   b = (1-tk).*b(:,2:end) + tk.*b(:,1:end-1);
end
p=b*c;