perimeterPen.py: copy PerimeterPen from symfont.py

Lib/fontTools/pens/perimeterPen.py

@@ -0,0 +1,39 @@
+"""Calculate the perimeter of a glyph."""
+
+from __future__ import print_function, division, absolute_import
+from fontTools.misc.py23 import *
+from fontTools.pens.basePen import BasePen
+from fontTools.misc.bezierTools import splitCubicAtT
+import math
+
+
+def distance(p0, p1):
+	return math.hypot(p0[0] - p1[0], p0[1] - p1[1])
+
+
+class PerimeterPen(BasePen):
+
+	def __init__(self, tolerance=0.005, glyphset=None):
+		BasePen.__init__(self, glyphset)
+		self.value = 0
+		self._mult = 1. + tolerance
+
+	def _moveTo(self, p0):
+		pass
+
+	def _lineTo(self, p1):
+		p0 = self._getCurrentPoint()
+		self.value += distance(p0, p1)
+
+	def _addCubic(self, p0, p1, p2, p3):
+		arch = distance(p0, p3)
+		box = distance(p0, p1) + distance(p1, p2) + distance(p2, p3)
+		if arch * self._mult >= box:
+			self.value += (arch + box) * .5
+		else:
+			for c in splitCubicAtT(p0, p1, p2, p3, .5):
+				self._addCubic(*c)
+
+	def _curveToOne(self, p1, p2, p3):
+		p0 = self._getCurrentPoint()
+		self._addCubic(p0, p1, p2, p3)