path.py 文件源码

def curvature(self, t):
        """returns the curvature of the segment at t."""
        return segment_curvature(self, t)

    # def icurvature(self, kappa):
    #     """returns a list of t-values such that 0 <= t<= 1 and
    #     seg.curvature(t) = kappa."""
    #
    #     a, b = self.radius.real, self.radius.imag
    #     if kappa > min(a, b)/max(a, b)**2 or kappa <= 0:
    #         return []
    #     if a==b:
    #         if kappa != 1/a:
    #             return []
    #         else:
    #             raise ValueError(
    #                 "The .icurvature() method for Arc elements with "
    #                 "radius.real == radius.imag (i.e. circle segments) "
    #                 "will raise this exception when kappa is 1/radius.real as "
    #                 "this is true at every point on the circle segment.")
    #
    #     # kappa = a*b / (a^2sin^2(tau) + b^2cos^2(tau))^(3/2), tau=2*pi*phase
    #     sin2 = np.poly1d([1, 0])
    #     p = kappa**2*(a*sin2 + b*(1 - sin2))**3 - a*b
    #     sin2s = polyroots01(p)
    #     taus = []
    #
    #     for sin2 in sin2s:
    #         taus += [np.arcsin(sqrt(sin2)), np.arcsin(-sqrt(sin2))]
    #
    #     # account for the other branch of arcsin
    #     sgn = lambda x: x/abs(x) if x else 0
    #     other_taus = [sgn(tau)*np.pi - tau for tau in taus if abs(tau) != np.pi/2]
    #     taus = taus + other_taus
    #
    #     # get rid of points not included in segment
    #     ts = [phase2t(tau) for tau in taus]
    #
    #     return [t for t in ts if 0<=t<=1]