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