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[varLib.models] Document a bit

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This commit is contained in:
Behdad Esfahbod 2023-12-07 13:01:48 -07:00
parent e98cec3264
commit ae69c22df8
1 changed files with 17 additions and 0 deletions
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17
Lib/fontTools/varLib/models.py
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@ -471,6 +471,10 @@ class VariationModel(object):
return model.getDeltas(items, round=round), model.supports return model.getDeltas(items, round=round), model.supports
def getScalars(self, loc): def getScalars(self, loc):
"""Return scalars for each delta, for the given location.
If interpolating many master-values at the same location,
this function allows speed up by fetching the scalars once
and using them with interpolateFromMastersAndScalars()"""
return [ return [
supportScalar( supportScalar(
loc, support, extrapolate=self.extrapolate, axisRanges=self.axisRanges loc, support, extrapolate=self.extrapolate, axisRanges=self.axisRanges
@ -479,6 +483,13 @@ class VariationModel(object):
] ]
def getMasterScalars(self, targetLocation): def getMasterScalars(self, targetLocation):
"""Return multipliers for each master, for the given location.
If interpolating many master-values at the same location,
this function allows speed up by fetching the scalars once.
Note that the scalars used in interpolateFromMastersAndScalars(),
are *not* the same as the ones returned here. They are the result
of getScalars()."""
out = self.getScalars(targetLocation) out = self.getScalars(targetLocation)
for i, weights in reversed(list(enumerate(self.deltaWeights))): for i, weights in reversed(list(enumerate(self.deltaWeights))):
for j, weight in weights.items(): for j, weight in weights.items():
@ -489,6 +500,7 @@ class VariationModel(object):
@staticmethod @staticmethod
def interpolateFromDeltasAndScalars(deltas, scalars): def interpolateFromDeltasAndScalars(deltas, scalars):
"""Interpolate from deltas and scalars fetched from getScalars()."""
v = None v = None
assert len(deltas) == len(scalars) assert len(deltas) == len(scalars)
for delta, scalar in zip(deltas, scalars): for delta, scalar in zip(deltas, scalars):
@ -502,14 +514,19 @@ class VariationModel(object):
return v return v
def interpolateFromDeltas(self, loc, deltas): def interpolateFromDeltas(self, loc, deltas):
"""Interpolate from deltas, at location loc."""
scalars = self.getScalars(loc) scalars = self.getScalars(loc)
return self.interpolateFromDeltasAndScalars(deltas, scalars) return self.interpolateFromDeltasAndScalars(deltas, scalars)
def interpolateFromMasters(self, loc, masterValues, *, round=noRound): def interpolateFromMasters(self, loc, masterValues, *, round=noRound):
"""Interpolate from master-values, at location loc."""
deltas = self.getDeltas(masterValues, round=round) deltas = self.getDeltas(masterValues, round=round)
return self.interpolateFromDeltas(loc, deltas) return self.interpolateFromDeltas(loc, deltas)
def interpolateFromMastersAndScalars(self, masterValues, scalars, *, round=noRound): def interpolateFromMastersAndScalars(self, masterValues, scalars, *, round=noRound):
"""Interpolate from master-values, and scalars fetched from
getScalars(), which is useful when you want to interpolate
multiple master-values with the same location."""
deltas = self.getDeltas(masterValues, round=round) deltas = self.getDeltas(masterValues, round=round)
return self.interpolateFromDeltasAndScalars(deltas, scalars) return self.interpolateFromDeltasAndScalars(deltas, scalars)