line_intersection.py

import numpy as np

def main():
    print intersectLines([0.,2.], [1.,1.], [3.,3.], [-1., -5.])
    

def intersectLines(s1, e1, s2, e2):
    # Append 1 to all points. Make them (x, y, 1)
    s1, e1, s2, e2 = [np.append(p, 1) for p in [s1, e1, s2, e2]]

    # Equations of lines :O!
    # (a, b, c) in: ax + by + c = 0
    l1 = np.cross(s1, e1)
    l2 = np.cross(s2, e2)

    # Intersection (:O :O)
    # (kx, ky, k).
    # If k is 0, then no intersection/ intersection at 'infinity' (:O)
    kx, ky, k = np.cross(l1, l2)
    return [kx/k, ky/k]

main()