# -*- 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])
[docs]
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))