Source Code for Module visgraph.drawing.catmullrom

 1   
 2 -def spline4p(t, p_1, p0, p1, p2): 
 3      x_1a = t * ((2-t) * t - 1) * p_1[0] 
 4      x_1b = t * ((2-t) * t - 1) * p_1[1] 
 5   
 6      x0a  = (t * t * (3 * t - 5) + 2) * p0[0] 
 7      x0b  = (t * t * (3 * t - 5) + 2) * p0[1] 
 8   
 9      x1a  = t * ((4 - 3 * t) * t + 1) * p1[0] 
10      x1b  = t * ((4 - 3 * t) * t + 1) * p1[1] 
11   
12      x2a  = (t - 1) * t * t * p2[0] 
13      x2b  = (t - 1) * t * t * p2[1] 
14   
15      final = ( (x_1a + x0a + x1a + x2a) / 2, 
16                (x_1b + x0b + x1b + x2b) / 2) 
17   
18      return final 
19   
20 -def calculate_catmullrom(points, steps = 30): 
21      ret = [] 
22      percents = [ step / float(steps) for step in range(steps) ] 
23      for i in xrange(1, len(points) - 2): 
24          for t in percents: 
25              ret.append(spline4p(t, points[i-1], points[i], points[i+1], points[i+2])) 
26      return ret 
27