find the closest point on a line to a given point

find_closest_point.py

def get_closest_point(a, b, p, clamp_to_segment=True):
    """ get closest point on line segment [ab] to point p  """
    ab = b - a  # vector from a -> b
    ap = p - a  # vector from a -> p
    ab2 = ab.x ** 2 + ab.y ** 2  # length of ab
    ap_dot_ab = ap.x * ab.x + ap.y * ab.y  # dot product (project ap onto ab)
    t = ap_dot_ab / ab2 
    if clamp_to_segment:
        if t < 0:
            t = 0
        elif t > 1:
            t = 1
    closest = a + ab * t
    return closest