Merge pull request #618 from anthrotype/area-pen

Area and Perimeter pens

Lib/fontTools/pens/areaPen.py

@@ -0,0 +1,57 @@
+"""Calculate the area of a glyph."""
+
+from __future__ import print_function, division, absolute_import
+from fontTools.misc.py23 import *
+from fontTools.pens.basePen import BasePen
+
+
+def polygon_area(p0, p1):
+	return -(p1[0] - p0[0]) * (p1[1] + p0[1]) * 0.5
+
+
+def quadratic_curve_area(p0, p1, p2):
+	x0, y0 = p0[0], p0[1]
+	x1, y1 = p1[0] - x0, p1[1] - y0
+	x2, y2 = p2[0] - x0, p2[1] - y0
+	return (x1*y2 - x2*y1) / 3
+
+
+def cubic_curve_area(p0, p1, p2, p3):
+	x0, y0 = p0[0], p0[1]
+	x1, y1 = p1[0] - x0, p1[1] - y0
+	x2, y2 = p2[0] - x0, p2[1] - y0
+	x3, y3 = p3[0] - x0, p3[1] - y0
+	return -(
+		x1 * (   -   y2 -   y3) +
+		x2 * (y1        - 2*y3) +
+		x3 * (y1 + 2*y2       )
+	) * 0.15
+
+
+class AreaPen(BasePen):
+
+	def __init__(self, glyphset=None):
+		BasePen.__init__(self, glyphset)
+		self.value = 0
+
+	def _moveTo(self, p0):
+		self.__startPoint = p0
+
+	def _lineTo(self, p1):
+		p0 = self._getCurrentPoint()
+		self.value += polygon_area(p0, p1)
+
+	def _curveToOne(self, p1, p2, p3):
+		p0 = self._getCurrentPoint()
+		self.value += cubic_curve_area(p0, p1, p2, p3)
+		self.value += polygon_area(p0, p3)
+
+	def _qCurveToOne(self, p1, p2):
+		p0 = self._getCurrentPoint()
+		self.value += quadratic_curve_area(p0, p1, p2)
+		self.value += polygon_area(p0, p2)
+
+	def _closePath(self):
+		p0 = self._getCurrentPoint()
+		if p0 != self.__startPoint:
+			self.value += polygon_area(p0, self.__startPoint)

Lib/fontTools/pens/perimeterPen.py

@@ -0,0 +1,44 @@
+"""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):
+		self.__startPoint = p0
+
+	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)
+
+	def _closePath(self):
+		p0 = self._getCurrentPoint()
+		if p0 != self.__startPoint:
+			self.value += distance(p0, self.__startPoint)