art2polyarea.py 文件源码

def _Angle(u, v):
    """Return angle between two vectors.

    Args:
      u: (float, float)
      v: (float, float)
    Returns:
      float - angle in radians between u and v, where
        it is +/- depending on sign of ux * vy - uy * vx
    """

    (ux, uy) = u
    (vx, vy) = v
    costheta = (ux * vx + uy * vy) / \
        (math.sqrt(ux ** 2 + uy ** 2) * math.sqrt(vx ** 2 + vy ** 2))
    if costheta > 1.0:
        costheta = 1.0
    if costheta < -1.0:
        costheta = -1.0
    theta = math.acos(costheta)
    if ux * vy - uy * vx < 0.0:
        theta = -theta
    return theta