# Copyright 2016 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import operator
from fontTools.cu2qu import curve_to_quadratic, curves_to_quadratic
from fontTools.pens.basePen import decomposeSuperBezierSegment
from fontTools.pens.filterPen import FilterPen
from fontTools.pens.reverseContourPen import ReverseContourPen
from fontTools.pens.pointPen import BasePointToSegmentPen
from fontTools.pens.pointPen import ReverseContourPointPen
[docs]
class Cu2QuPen(FilterPen):
"""A filter pen to convert cubic bezier curves to quadratic b-splines
using the FontTools SegmentPen protocol.
Args:
other_pen: another SegmentPen used to draw the transformed outline.
max_err: maximum approximation error in font units. For optimal results,
if you know the UPEM of the font, we recommend setting this to a
value equal, or close to UPEM / 1000.
reverse_direction: flip the contours' direction but keep starting point.
stats: a dictionary counting the point numbers of quadratic segments.
all_quadratic: if True (default), only quadratic b-splines are generated.
if False, quadratic curves or cubic curves are generated depending
on which one is more economical.
"""
def __init__(
self,
other_pen,
max_err,
reverse_direction=False,
stats=None,
all_quadratic=True,
):
if reverse_direction:
other_pen = ReverseContourPen(other_pen)
super().__init__(other_pen)
self.max_err = max_err
self.stats = stats
self.all_quadratic = all_quadratic
def _convert_curve(self, pt1, pt2, pt3):
curve = (self.current_pt, pt1, pt2, pt3)
result = curve_to_quadratic(curve, self.max_err, self.all_quadratic)
if self.stats is not None:
n = str(len(result) - 2)
self.stats[n] = self.stats.get(n, 0) + 1
if self.all_quadratic:
self.qCurveTo(*result[1:])
else:
if len(result) == 3:
self.qCurveTo(*result[1:])
else:
assert len(result) == 4
super().curveTo(*result[1:])
[docs]
def curveTo(self, *points):
n = len(points)
if n == 3:
# this is the most common case, so we special-case it
self._convert_curve(*points)
elif n > 3:
for segment in decomposeSuperBezierSegment(points):
self._convert_curve(*segment)
else:
self.qCurveTo(*points)
[docs]
class Cu2QuPointPen(BasePointToSegmentPen):
"""A filter pen to convert cubic bezier curves to quadratic b-splines
using the FontTools PointPen protocol.
Args:
other_point_pen: another PointPen used to draw the transformed outline.
max_err: maximum approximation error in font units. For optimal results,
if you know the UPEM of the font, we recommend setting this to a
value equal, or close to UPEM / 1000.
reverse_direction: reverse the winding direction of all contours.
stats: a dictionary counting the point numbers of quadratic segments.
all_quadratic: if True (default), only quadratic b-splines are generated.
if False, quadratic curves or cubic curves are generated depending
on which one is more economical.
"""
__points_required = {
"move": (1, operator.eq),
"line": (1, operator.eq),
"qcurve": (2, operator.ge),
"curve": (3, operator.eq),
}
def __init__(
self,
other_point_pen,
max_err,
reverse_direction=False,
stats=None,
all_quadratic=True,
):
BasePointToSegmentPen.__init__(self)
if reverse_direction:
self.pen = ReverseContourPointPen(other_point_pen)
else:
self.pen = other_point_pen
self.max_err = max_err
self.stats = stats
self.all_quadratic = all_quadratic
def _flushContour(self, segments):
assert len(segments) >= 1
closed = segments[0][0] != "move"
new_segments = []
prev_points = segments[-1][1]
prev_on_curve = prev_points[-1][0]
for segment_type, points in segments:
if segment_type == "curve":
for sub_points in self._split_super_bezier_segments(points):
on_curve, smooth, name, kwargs = sub_points[-1]
bcp1, bcp2 = sub_points[0][0], sub_points[1][0]
cubic = [prev_on_curve, bcp1, bcp2, on_curve]
quad = curve_to_quadratic(cubic, self.max_err, self.all_quadratic)
if self.stats is not None:
n = str(len(quad) - 2)
self.stats[n] = self.stats.get(n, 0) + 1
new_points = [(pt, False, None, {}) for pt in quad[1:-1]]
new_points.append((on_curve, smooth, name, kwargs))
if self.all_quadratic or len(new_points) == 2:
new_segments.append(["qcurve", new_points])
else:
new_segments.append(["curve", new_points])
prev_on_curve = sub_points[-1][0]
else:
new_segments.append([segment_type, points])
prev_on_curve = points[-1][0]
if closed:
# the BasePointToSegmentPen.endPath method that calls _flushContour
# rotates the point list of closed contours so that they end with
# the first on-curve point. We restore the original starting point.
new_segments = new_segments[-1:] + new_segments[:-1]
self._drawPoints(new_segments)
def _split_super_bezier_segments(self, points):
sub_segments = []
# n is the number of control points
n = len(points) - 1
if n == 2:
# a simple bezier curve segment
sub_segments.append(points)
elif n > 2:
# a "super" bezier; decompose it
on_curve, smooth, name, kwargs = points[-1]
num_sub_segments = n - 1
for i, sub_points in enumerate(
decomposeSuperBezierSegment([pt for pt, _, _, _ in points])
):
new_segment = []
for point in sub_points[:-1]:
new_segment.append((point, False, None, {}))
if i == (num_sub_segments - 1):
# the last on-curve keeps its original attributes
new_segment.append((on_curve, smooth, name, kwargs))
else:
# on-curves of sub-segments are always "smooth"
new_segment.append((sub_points[-1], True, None, {}))
sub_segments.append(new_segment)
else:
raise AssertionError("expected 2 control points, found: %d" % n)
return sub_segments
def _drawPoints(self, segments):
pen = self.pen
pen.beginPath()
last_offcurves = []
points_required = self.__points_required
for i, (segment_type, points) in enumerate(segments):
if segment_type in points_required:
n, op = points_required[segment_type]
assert op(len(points), n), (
f"illegal {segment_type!r} segment point count: "
f"expected {n}, got {len(points)}"
)
offcurves = points[:-1]
if i == 0:
# any off-curve points preceding the first on-curve
# will be appended at the end of the contour
last_offcurves = offcurves
else:
for pt, smooth, name, kwargs in offcurves:
pen.addPoint(pt, None, smooth, name, **kwargs)
pt, smooth, name, kwargs = points[-1]
if pt is None:
assert segment_type == "qcurve"
# special quadratic contour with no on-curve points:
# we need to skip the "None" point. See also the Pen
# protocol's qCurveTo() method and fontTools.pens.basePen
pass
else:
pen.addPoint(pt, segment_type, smooth, name, **kwargs)
else:
raise AssertionError("unexpected segment type: %r" % segment_type)
for pt, smooth, name, kwargs in last_offcurves:
pen.addPoint(pt, None, smooth, name, **kwargs)
pen.endPath()
[docs]
def addComponent(self, baseGlyphName, transformation):
assert self.currentPath is None
self.pen.addComponent(baseGlyphName, transformation)
[docs]
class Cu2QuMultiPen:
"""A filter multi-pen to convert cubic bezier curves to quadratic b-splines
in a interpolation-compatible manner, using the FontTools SegmentPen protocol.
Args:
other_pens: list of SegmentPens used to draw the transformed outlines.
max_err: maximum approximation error in font units. For optimal results,
if you know the UPEM of the font, we recommend setting this to a
value equal, or close to UPEM / 1000.
reverse_direction: flip the contours' direction but keep starting point.
This pen does not follow the normal SegmentPen protocol. Instead, its
moveTo/lineTo/qCurveTo/curveTo methods take a list of tuples that are
arguments that would normally be passed to a SegmentPen, one item for
each of the pens in other_pens.
"""
# TODO Simplify like 3e8ebcdce592fe8a59ca4c3a294cc9724351e1ce
# Remove start_pts and _add_moveTO
def __init__(self, other_pens, max_err, reverse_direction=False):
if reverse_direction:
other_pens = [
ReverseContourPen(pen, outputImpliedClosingLine=True)
for pen in other_pens
]
self.pens = other_pens
self.max_err = max_err
self.start_pts = None
self.current_pts = None
def _check_contour_is_open(self):
if self.current_pts is None:
raise AssertionError("moveTo is required")
def _check_contour_is_closed(self):
if self.current_pts is not None:
raise AssertionError("closePath or endPath is required")
def _add_moveTo(self):
if self.start_pts is not None:
for pt, pen in zip(self.start_pts, self.pens):
pen.moveTo(*pt)
self.start_pts = None
[docs]
def moveTo(self, pts):
self._check_contour_is_closed()
self.start_pts = self.current_pts = pts
self._add_moveTo()
[docs]
def lineTo(self, pts):
self._check_contour_is_open()
self._add_moveTo()
for pt, pen in zip(pts, self.pens):
pen.lineTo(*pt)
self.current_pts = pts
[docs]
def qCurveTo(self, pointsList):
self._check_contour_is_open()
if len(pointsList[0]) == 1:
self.lineTo([(points[0],) for points in pointsList])
return
self._add_moveTo()
current_pts = []
for points, pen in zip(pointsList, self.pens):
pen.qCurveTo(*points)
current_pts.append((points[-1],))
self.current_pts = current_pts
def _curves_to_quadratic(self, pointsList):
curves = []
for current_pt, points in zip(self.current_pts, pointsList):
curves.append(current_pt + points)
quadratics = curves_to_quadratic(curves, [self.max_err] * len(curves))
pointsList = []
for quadratic in quadratics:
pointsList.append(quadratic[1:])
self.qCurveTo(pointsList)
[docs]
def curveTo(self, pointsList):
self._check_contour_is_open()
self._curves_to_quadratic(pointsList)
[docs]
def closePath(self):
self._check_contour_is_open()
if self.start_pts is None:
for pen in self.pens:
pen.closePath()
self.current_pts = self.start_pts = None
[docs]
def endPath(self):
self._check_contour_is_open()
if self.start_pts is None:
for pen in self.pens:
pen.endPath()
self.current_pts = self.start_pts = None
[docs]
def addComponent(self, glyphName, transformations):
self._check_contour_is_closed()
for trans, pen in zip(transformations, self.pens):
pen.addComponent(glyphName, trans)