57 lines
1.7 KiB
Python
57 lines
1.7 KiB
Python
"""The goal of this gist is to show how to compute many points on a path
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quickly using NumPy arrays. I.e. there's a much faster way than using, say
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[some_path.point(t) for t in many_tvals]. The example below assumes the
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`Path` object is composed entirely of `CubicBezier` objects, but this can
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easily be generalized to paths containing `Line` and `QuadraticBezier` objects
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also.
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Note: The relevant matrix transformation for quadratics can be found in the
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svgpathtools.bezier module."""
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import numpy as np
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from svgpathtools import *
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class HigherOrderBezier:
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def __init__(self, bpoints):
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self.bpts = bpoints
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def bpoints(self):
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return self.bpts
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def point(self, t):
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return bezier_point(self.bpoints(), t)
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def __repr__(self):
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return str(self.bpts)
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def random_bezier(degree):
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if degree <= 3:
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return bpoints2bezier(polynomial2bezier(np.random.rand(degree + 1)))
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else:
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return HigherOrderBezier(np.random.rand(degree + 1))
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def points_in_each_seg_slow(path, tvals):
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return [seg.poly()(tvals) for seg in path]
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def points_in_each_seg(path, tvals):
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"""Compute seg.point(t) for each seg in path and each t in tvals."""
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A = np.matrix([[-1, 3, -3, 1], # transforms cubic bez to standard poly
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[ 3, -6, 3, 0],
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[-3, 3, 0, 0],
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[ 1, 0, 0, 0]])
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B = [seg.bpoints() for seg in path]
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return np.dot(B, np.dot(A, np.power(tvals, [[3],[2],[1],[0]])))
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if __name__ == '__main__':
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num_segs = 1000
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testpath = Path(*[random_bezier(3) for dummy in range(num_segs)])
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tvals = np.linspace(0, 1, 10)
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pts = points_in_each_seg(testpath, tvals)
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pts_check = points_in_each_seg_slow(testpath, tvals)
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print np.max(pts - pts_check)
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