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