251 lines
7.9 KiB
Python
251 lines
7.9 KiB
Python
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""" Simplify TrueType glyphs by merging overlapping contours/components.
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Requires https://github.com/fonttools/skia-pathops
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"""
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import itertools
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import logging
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from typing import Callable, Iterable, Optional, Mapping
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from fontTools.misc.roundTools import otRound
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from fontTools.ttLib import ttFont
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from fontTools.ttLib.tables import _g_l_y_f
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from fontTools.ttLib.tables import _h_m_t_x
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from fontTools.pens.ttGlyphPen import TTGlyphPen
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import pathops
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__all__ = ["removeOverlaps"]
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class RemoveOverlapsError(Exception):
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pass
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log = logging.getLogger("fontTools.ttLib.removeOverlaps")
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_TTGlyphMapping = Mapping[str, ttFont._TTGlyph]
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def skPathFromGlyph(glyphName: str, glyphSet: _TTGlyphMapping) -> pathops.Path:
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path = pathops.Path()
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pathPen = path.getPen(glyphSet=glyphSet)
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glyphSet[glyphName].draw(pathPen)
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return path
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def skPathFromGlyphComponent(
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component: _g_l_y_f.GlyphComponent, glyphSet: _TTGlyphMapping
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):
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baseGlyphName, transformation = component.getComponentInfo()
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path = skPathFromGlyph(baseGlyphName, glyphSet)
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return path.transform(*transformation)
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def componentsOverlap(glyph: _g_l_y_f.Glyph, glyphSet: _TTGlyphMapping) -> bool:
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if not glyph.isComposite():
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raise ValueError("This method only works with TrueType composite glyphs")
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if len(glyph.components) < 2:
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return False # single component, no overlaps
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component_paths = {}
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def _get_nth_component_path(index: int) -> pathops.Path:
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if index not in component_paths:
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component_paths[index] = skPathFromGlyphComponent(
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glyph.components[index], glyphSet
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)
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return component_paths[index]
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return any(
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pathops.op(
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_get_nth_component_path(i),
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_get_nth_component_path(j),
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pathops.PathOp.INTERSECTION,
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fix_winding=False,
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keep_starting_points=False,
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)
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for i, j in itertools.combinations(range(len(glyph.components)), 2)
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)
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def ttfGlyphFromSkPath(path: pathops.Path) -> _g_l_y_f.Glyph:
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# Skia paths have no 'components', no need for glyphSet
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ttPen = TTGlyphPen(glyphSet=None)
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path.draw(ttPen)
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glyph = ttPen.glyph()
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assert not glyph.isComposite()
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# compute glyph.xMin (glyfTable parameter unused for non composites)
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glyph.recalcBounds(glyfTable=None)
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return glyph
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def _round_path(
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path: pathops.Path, round: Callable[[float], float] = otRound
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) -> pathops.Path:
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rounded_path = pathops.Path()
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for verb, points in path:
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rounded_path.add(verb, *((round(p[0]), round(p[1])) for p in points))
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return rounded_path
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def _simplify(path: pathops.Path, debugGlyphName: str) -> pathops.Path:
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# skia-pathops has a bug where it sometimes fails to simplify paths when there
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# are float coordinates and control points are very close to one another.
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# Rounding coordinates to integers works around the bug.
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# Since we are going to round glyf coordinates later on anyway, here it is
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# ok(-ish) to also round before simplify. Better than failing the whole process
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# for the entire font.
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# https://bugs.chromium.org/p/skia/issues/detail?id=11958
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# https://github.com/google/fonts/issues/3365
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# TODO(anthrotype): remove once this Skia bug is fixed
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try:
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return pathops.simplify(path, clockwise=path.clockwise)
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except pathops.PathOpsError:
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pass
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path = _round_path(path)
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try:
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path = pathops.simplify(path, clockwise=path.clockwise)
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log.debug(
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"skia-pathops failed to simplify '%s' with float coordinates, "
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"but succeded using rounded integer coordinates",
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debugGlyphName,
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)
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return path
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except pathops.PathOpsError as e:
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if log.isEnabledFor(logging.DEBUG):
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path.dump()
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raise RemoveOverlapsError(
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f"Failed to remove overlaps from glyph {debugGlyphName!r}"
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) from e
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raise AssertionError("Unreachable")
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def removeTTGlyphOverlaps(
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glyphName: str,
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glyphSet: _TTGlyphMapping,
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glyfTable: _g_l_y_f.table__g_l_y_f,
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hmtxTable: _h_m_t_x.table__h_m_t_x,
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removeHinting: bool = True,
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) -> bool:
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glyph = glyfTable[glyphName]
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# decompose composite glyphs only if components overlap each other
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if (
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glyph.numberOfContours > 0
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or glyph.isComposite()
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and componentsOverlap(glyph, glyphSet)
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):
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path = skPathFromGlyph(glyphName, glyphSet)
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# remove overlaps
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path2 = _simplify(path, glyphName)
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# replace TTGlyph if simplified path is different (ignoring contour order)
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if {tuple(c) for c in path.contours} != {tuple(c) for c in path2.contours}:
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glyfTable[glyphName] = glyph = ttfGlyphFromSkPath(path2)
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# simplified glyph is always unhinted
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assert not glyph.program
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# also ensure hmtx LSB == glyph.xMin so glyph origin is at x=0
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width, lsb = hmtxTable[glyphName]
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if lsb != glyph.xMin:
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hmtxTable[glyphName] = (width, glyph.xMin)
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return True
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if removeHinting:
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glyph.removeHinting()
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return False
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def removeOverlaps(
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font: ttFont.TTFont,
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glyphNames: Optional[Iterable[str]] = None,
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removeHinting: bool = True,
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ignoreErrors=False,
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) -> None:
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"""Simplify glyphs in TTFont by merging overlapping contours.
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Overlapping components are first decomposed to simple contours, then merged.
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Currently this only works with TrueType fonts with 'glyf' table.
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Raises NotImplementedError if 'glyf' table is absent.
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Note that removing overlaps invalidates the hinting. By default we drop hinting
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from all glyphs whether or not overlaps are removed from a given one, as it would
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look weird if only some glyphs are left (un)hinted.
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Args:
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font: input TTFont object, modified in place.
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glyphNames: optional iterable of glyph names (str) to remove overlaps from.
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By default, all glyphs in the font are processed.
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removeHinting (bool): set to False to keep hinting for unmodified glyphs.
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ignoreErrors (bool): set to True to ignore errors while removing overlaps,
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thus keeping the tricky glyphs unchanged (fonttools/fonttools#2363).
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"""
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try:
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glyfTable = font["glyf"]
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except KeyError:
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raise NotImplementedError("removeOverlaps currently only works with TTFs")
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hmtxTable = font["hmtx"]
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# wraps the underlying glyf Glyphs, takes care of interfacing with drawing pens
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glyphSet = font.getGlyphSet()
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if glyphNames is None:
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glyphNames = font.getGlyphOrder()
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# process all simple glyphs first, then composites with increasing component depth,
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# so that by the time we test for component intersections the respective base glyphs
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# have already been simplified
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glyphNames = sorted(
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glyphNames,
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key=lambda name: (
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(
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glyfTable[name].getCompositeMaxpValues(glyfTable).maxComponentDepth
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if glyfTable[name].isComposite()
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else 0
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),
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name,
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),
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)
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modified = set()
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for glyphName in glyphNames:
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try:
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if removeTTGlyphOverlaps(
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glyphName, glyphSet, glyfTable, hmtxTable, removeHinting
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):
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modified.add(glyphName)
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except RemoveOverlapsError:
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if not ignoreErrors:
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raise
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log.error("Failed to remove overlaps for '%s'", glyphName)
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log.debug("Removed overlaps for %s glyphs:\n%s", len(modified), " ".join(modified))
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def main(args=None):
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import sys
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if args is None:
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args = sys.argv[1:]
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if len(args) < 2:
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print(
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f"usage: fonttools ttLib.removeOverlaps INPUT.ttf OUTPUT.ttf [GLYPHS ...]"
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)
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sys.exit(1)
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src = args[0]
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dst = args[1]
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glyphNames = args[2:] or None
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with ttFont.TTFont(src) as f:
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removeOverlaps(f, glyphNames)
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f.save(dst)
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if __name__ == "__main__":
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main()
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