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[GX] Optimize ‘gvar’ tables for tuples affecting all points in a glyph

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After this change, round-tripping through TTX shrinks the size of all
our test fonts. Specifically, Skia.ttf shrinks from 478K to 473K,
JamRegular.ttf from 113K to 107K, and BuffaloGalRegular from 67K to 61K.
This commit is contained in:
Sascha Brawer 2015-06-10 11:19:06 +02:00
parent 4bbc1f7e83
commit 7f6d2af45a
2 changed files with 14 additions and 8 deletions
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5
Lib/fontTools/ttLib/tables/_g_v_a_r.py
View File

@ -490,6 +490,11 @@ class GlyphVariation(object):
@staticmethod
def compilePoints(points, numPointsInGlyph):
# If the set consists of all points in the glyph, it gets encoded with
# a special encoding: a single zero byte.
if len(points) == numPointsInGlyph:
return b"\0"
# In the 'gvar' table, the packing of point numbers is a little surprising.
# It consists of multiple runs, each being a delta-encoded list of integers.
# For example, the point set {17, 18, 19, 20, 21, 22, 23} gets encoded as

17
Lib/fontTools/ttLib/tables/_g_v_a_r_test.py
View File

@ -271,8 +271,8 @@ class GlyphVariationTest(unittest.TestCase):
tuple, data = gvar.compile(axisTags, sharedCoordIndices, sharedPoints=None)
# len(data)=13; flags=PRIVATE_POINT_NUMBERS; tupleIndex=0x77
# embeddedCoord=[]; intermediateCoord=[]
self.assertEqual("00 0D 20 77", hexencode(tuple))
self.assertEqual("03 02 00 01 01 " # 3 points: [0, 1, 2]
self.assertEqual("00 09 20 77", hexencode(tuple))
self.assertEqual("00 " # all points in glyph
"02 07 08 09 " # deltaX: [7, 8, 9]
"02 04 05 06", # deltaY: [4, 5, 6]
hexencode(data))
@ -285,8 +285,8 @@ class GlyphVariationTest(unittest.TestCase):
tuple, data = gvar.compile(axisTags, sharedCoordIndices, sharedPoints=None)
# len(data)=13; flags=PRIVATE_POINT_NUMBERS; tupleIndex=0x77
# embeddedCoord=[]; intermediateCoord=[(0.0, 0.0), (1.0, 1.0)]
self.assertEqual("00 0D 60 77 00 00 00 00 40 00 40 00", hexencode(tuple))
self.assertEqual("03 02 00 01 01 " # 3 points: [0, 1, 2]
self.assertEqual("00 09 60 77 00 00 00 00 40 00 40 00", hexencode(tuple))
self.assertEqual("00 " # all points in glyph
"02 07 08 09 " # deltaX: [7, 8, 9]
"02 04 05 06", # deltaY: [4, 5, 6]
hexencode(data))
@ -322,8 +322,8 @@ class GlyphVariationTest(unittest.TestCase):
tuple, data = gvar.compile(axisTags, sharedCoordIndices={}, sharedPoints=None)
# len(data)=13; flags=PRIVATE_POINT_NUMBERS|EMBEDDED_TUPLE_COORD
# embeddedCoord=[(0.5, 0.8)]; intermediateCoord=[]
self.assertEqual("00 0D A0 00 20 00 33 33", hexencode(tuple))
self.assertEqual("03 02 00 01 01 " # 3 points: [0, 1, 2]
self.assertEqual("00 09 A0 00 20 00 33 33", hexencode(tuple))
self.assertEqual("00 " # all points in glyph
"02 07 08 09 " # deltaX: [7, 8, 9]
"02 04 05 06", # deltaY: [4, 5, 6]
hexencode(data))
@ -335,8 +335,8 @@ class GlyphVariationTest(unittest.TestCase):
tuple, data = gvar.compile(axisTags, sharedCoordIndices={}, sharedPoints=None)
# len(data)=13; flags=PRIVATE_POINT_NUMBERS|INTERMEDIATE_TUPLE|EMBEDDED_TUPLE_COORD
# embeddedCoord=(0.5, 0.8); intermediateCoord=[(0.4, 0.7), (0.6, 0.9)]
self.assertEqual("00 0D E0 00 20 00 33 33 19 9A 2C CD 26 66 39 9A", hexencode(tuple))
self.assertEqual("03 02 00 01 01 " # 3 points: [0, 1, 2]
self.assertEqual("00 09 E0 00 20 00 33 33 19 9A 2C CD 26 66 39 9A", hexencode(tuple))
self.assertEqual("00 " # all points in glyph
"02 07 08 09 " # deltaX: [7, 8, 9]
"02 04 05 06", # deltaY: [4, 5, 6]
hexencode(data))
@ -380,6 +380,7 @@ class GlyphVariationTest(unittest.TestCase):
def test_compilePoints(self):
compilePoints = lambda p: GlyphVariation.compilePoints(set(p), numPointsInGlyph=999)
self.assertEqual("00", hexencode(compilePoints(range(999)))) # all points in glyph
self.assertEqual("01 00 07", hexencode(compilePoints([7])))
self.assertEqual("01 80 FF FF", hexencode(compilePoints([65535])))
self.assertEqual("02 01 09 06", hexencode(compilePoints([9, 15])))