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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)) | |