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comparison python/utils.py @ 24:6fb59cfb201e

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first version of segmentIntersection
author Nicolas Saunier <nico@confins.net>
date Sat, 05 Dec 2009 11:04:03 -0500
parents 5a21d2cfee44
children 44689029a86f
comparison
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23:5f2921ad4f7e 24:6fb59cfb201e
5 #from pylab import * 5 #from pylab import *
6 6
7 __metaclass__ = type 7 __metaclass__ = type
8 8
9 commentChar = '#'; 9 commentChar = '#';
10
11 # maths
12
13 def segmentIntersection(s1, s2):
14 '''Returns the intersecting point, None otherwise
15 format for a segment is [[x1, x2], [y1,y2]]
16
17 >>> segmentIntersection([[0, 1], [0,1]], [[0, 1], [1,2]])
18 >>> segmentIntersection([[0, 1], [1,0]], [[0, 1], [2,1]])
19 >>> segmentIntersection([[0, 2], [0,0]], [[1, 1], [-1,1]])
20 [1.0, 0.0]
21 >>> segmentIntersection([[0, 2], [0,0]], [[1, 1], [1,2]])
22 '''
23 from numpy import matrix
24 from numpy.linalg import linalg, det
25
26 ds1 = [s1[0][1]-s1[0][0], s1[1][1]-s1[1][0]]
27 ds2 = [s2[0][1]-s2[0][0], s2[1][1]-s2[1][0]]
28
29 A = matrix([[ds1[1], -ds1[0]],
30 [ds2[1], -ds2[0]]])
31 B = matrix([[ds1[1]*s1[0][0]-ds1[0]*s1[1][0]],
32 [ds2[1]*s2[0][0]-ds2[0]*s2[1][0]]])
33
34 if linalg.det(A) == 0:#crossProduct(ds1, ds2) == 0:
35 return None
36 else:
37 intersection = linalg.solve(A,B)
38 if (intersection[0,0] >= s1[0][0] and intersection[0,0] <= s1[0][1]
39 and intersection[0,0] >= s2[0][0] and intersection[0,0] <= s2[0][1]
40 and intersection[1,0] >= s1[1][0] and intersection[1,0] <= s1[1][1]
41 and intersection[1,0] >= s2[1][0] and intersection[1,0] <= s2[1][1]):
42 return [intersection[0,0], intersection[1,0]]
43 else:
44 return None
45
46 def crossProduct(l1, l2):
47 return l1[0]*l2[1]-l1[1]*l2[0]
48
49 # file I/O
10 50
11 def openCheck(filename, option = 'r', quit = False): 51 def openCheck(filename, option = 'r', quit = False):
12 '''Open file filename in read mode by default 52 '''Open file filename in read mode by default
13 and checks it is open 53 and checks it is open
14 54