90 lines
3.5 KiB
Python
90 lines
3.5 KiB
Python
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# Modified from https://github.com/adobe-type-tools/psautohint/blob/08b346865710ed3c172f1eb581d6ef243b203f99/python/psautohint/ufoFont.py#L800-L838
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import hashlib
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from fontTools.pens.basePen import MissingComponentError
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from fontTools.pens.pointPen import AbstractPointPen
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class HashPointPen(AbstractPointPen):
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"""
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This pen can be used to check if a glyph's contents (outlines plus
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components) have changed.
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Components are added as the original outline plus each composite's
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transformation.
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Example: You have some TrueType hinting code for a glyph which you want to
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compile. The hinting code specifies a hash value computed with HashPointPen
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that was valid for the glyph's outlines at the time the hinting code was
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written. Now you can calculate the hash for the glyph's current outlines to
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check if the outlines have changed, which would probably make the hinting
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code invalid.
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> glyph = ufo[name]
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> hash_pen = HashPointPen(glyph.width, ufo)
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> glyph.drawPoints(hash_pen)
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> ttdata = glyph.lib.get("public.truetype.instructions", None)
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> stored_hash = ttdata.get("id", None) # The hash is stored in the "id" key
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> if stored_hash is None or stored_hash != hash_pen.hash:
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> logger.error(f"Glyph hash mismatch, glyph '{name}' will have no instructions in font.")
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> else:
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> # The hash values are identical, the outline has not changed.
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> # Compile the hinting code ...
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> pass
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If you want to compare a glyph from a source format which supports floating point
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coordinates and transformations against a glyph from a format which has restrictions
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on the precision of floats, e.g. UFO vs. TTF, you must use an appropriate rounding
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function to make the values comparable. For TTF fonts with composites, this
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construct can be used to make the transform values conform to F2Dot14:
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> ttf_hash_pen = HashPointPen(ttf_glyph_width, ttFont.getGlyphSet())
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> ttf_round_pen = RoundingPointPen(ttf_hash_pen, transformRoundFunc=partial(floatToFixedToFloat, precisionBits=14))
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> ufo_hash_pen = HashPointPen(ufo_glyph.width, ufo)
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> ttf_glyph.drawPoints(ttf_round_pen, ttFont["glyf"])
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> ufo_round_pen = RoundingPointPen(ufo_hash_pen, transformRoundFunc=partial(floatToFixedToFloat, precisionBits=14))
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> ufo_glyph.drawPoints(ufo_round_pen)
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> assert ttf_hash_pen.hash == ufo_hash_pen.hash
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"""
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def __init__(self, glyphWidth=0, glyphSet=None):
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self.glyphset = glyphSet
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self.data = ["w%s" % round(glyphWidth, 9)]
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@property
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def hash(self):
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data = "".join(self.data)
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if len(data) >= 128:
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data = hashlib.sha512(data.encode("ascii")).hexdigest()
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return data
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def beginPath(self, identifier=None, **kwargs):
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pass
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def endPath(self):
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self.data.append("|")
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def addPoint(
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self,
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pt,
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segmentType=None,
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smooth=False,
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name=None,
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identifier=None,
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**kwargs,
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):
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if segmentType is None:
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pt_type = "o" # offcurve
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else:
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pt_type = segmentType[0]
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self.data.append(f"{pt_type}{pt[0]:g}{pt[1]:+g}")
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def addComponent(self, baseGlyphName, transformation, identifier=None, **kwargs):
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tr = "".join([f"{t:+}" for t in transformation])
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self.data.append("[")
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try:
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self.glyphset[baseGlyphName].drawPoints(self)
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except KeyError:
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raise MissingComponentError(baseGlyphName)
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self.data.append(f"({tr})]")
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