| # -*- 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)) |
