38 lines
1.2 KiB
Python
38 lines
1.2 KiB
Python
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import math
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from inkex import EffectExtension, PathElement, transforms as T
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# https://en.wikipedia.org/wiki/Rotations_and_reflections_in_two_dimensions
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def reflection_matrix(theta):
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theta2 = 2 * theta
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return [
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[math.cos(theta2), math.sin(theta2), 0],
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[math.sin(theta2), -math.cos(theta2), 0],
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]
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def svg_matrix_order(mat):
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((a, c, e), (b, d, f)) = mat
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return a, b, c, d, e, f
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class Flip(EffectExtension):
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"""Extension to flip a path about the line from the start to end node"""
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def effect(self):
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for node in self.svg.selection.filter(PathElement).values():
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points = list(node.path.end_points)
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if len(points) < 2 or points[0] == points[-1]:
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continue
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start = points[0]
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end = points[-1]
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v = end - start
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theta = math.atan2(v.y, v.x)
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# transforms go in reverse order
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mat = T.Transform()
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mat.add_translate(start)
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mat.add_matrix(*svg_matrix_order(reflection_matrix(theta)))
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mat.add_translate(-start)
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node.path = node.path.transform(mat)
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if __name__ == '__main__':
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Flip().run()
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