70 lines
2.1 KiB
Python
70 lines
2.1 KiB
Python
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# -*- coding: utf-8 -*-
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"""Calculate the perimeter of a glyph."""
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from fontTools.pens.basePen import BasePen
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from fontTools.misc.bezierTools import (
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approximateQuadraticArcLengthC,
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calcQuadraticArcLengthC,
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approximateCubicArcLengthC,
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calcCubicArcLengthC,
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)
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import math
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__all__ = ["PerimeterPen"]
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def _distance(p0, p1):
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return math.hypot(p0[0] - p1[0], p0[1] - p1[1])
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class PerimeterPen(BasePen):
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def __init__(self, glyphset=None, tolerance=0.005):
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BasePen.__init__(self, glyphset)
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self.value = 0
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self.tolerance = tolerance
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# Choose which algorithm to use for quadratic and for cubic.
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# Quadrature is faster but has fixed error characteristic with no strong
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# error bound. The cutoff points are derived empirically.
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self._addCubic = (
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self._addCubicQuadrature if tolerance >= 0.0015 else self._addCubicRecursive
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)
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self._addQuadratic = (
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self._addQuadraticQuadrature
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if tolerance >= 0.00075
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else self._addQuadraticExact
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)
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def _moveTo(self, p0):
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self.__startPoint = p0
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def _closePath(self):
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p0 = self._getCurrentPoint()
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if p0 != self.__startPoint:
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self._lineTo(self.__startPoint)
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def _lineTo(self, p1):
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p0 = self._getCurrentPoint()
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self.value += _distance(p0, p1)
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def _addQuadraticExact(self, c0, c1, c2):
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self.value += calcQuadraticArcLengthC(c0, c1, c2)
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def _addQuadraticQuadrature(self, c0, c1, c2):
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self.value += approximateQuadraticArcLengthC(c0, c1, c2)
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def _qCurveToOne(self, p1, p2):
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p0 = self._getCurrentPoint()
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self._addQuadratic(complex(*p0), complex(*p1), complex(*p2))
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def _addCubicRecursive(self, c0, c1, c2, c3):
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self.value += calcCubicArcLengthC(c0, c1, c2, c3, self.tolerance)
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def _addCubicQuadrature(self, c0, c1, c2, c3):
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self.value += approximateCubicArcLengthC(c0, c1, c2, c3)
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def _curveToOne(self, p1, p2, p3):
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p0 = self._getCurrentPoint()
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self._addCubic(complex(*p0), complex(*p1), complex(*p2), complex(*p3))
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