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from fontTools.misc import sstruct
from fontTools.misc.textTools import safeEval, num2binary, binary2num
from . import DefaultTable
from .sbixStrike import Strike
sbixHeaderFormat = """
>
version: H # Version number (set to 1)
flags: H # The only two bits used in the flags field are bits 0
# and 1. For historical reasons, bit 0 must always be 1.
# Bit 1 is a sbixDrawOutlines flag and is interpreted as
# follows:
# 0: Draw only 'sbix' bitmaps
# 1: Draw both 'sbix' bitmaps and outlines, in that
# order
numStrikes: L # Number of bitmap strikes to follow
"""
sbixHeaderFormatSize = sstruct.calcsize(sbixHeaderFormat)
sbixStrikeOffsetFormat = """
>
strikeOffset: L # Offset from begining of table to data for the
# individual strike
"""
sbixStrikeOffsetFormatSize = sstruct.calcsize(sbixStrikeOffsetFormat)
class table__s_b_i_x(DefaultTable.DefaultTable):
"""Standard Bitmap Graphics table
The ``sbix`` table stores bitmap image data in standard graphics formats
like JPEG, PNG, or TIFF. The glyphs for which the ``sbix`` table provides
data are indexed by Glyph ID. For each such glyph, the ``sbix`` table can
hold different data for different sizes, called "strikes."
See also https://learn.microsoft.com/en-us/typography/opentype/spec/sbix
"""
def __init__(self, tag=None):
DefaultTable.DefaultTable.__init__(self, tag)
self.version = 1
self.flags = 1
self.numStrikes = 0
self.strikes = {}
self.strikeOffsets = []
def decompile(self, data, ttFont):
# read table header
sstruct.unpack(sbixHeaderFormat, data[:sbixHeaderFormatSize], self)
# collect offsets to individual strikes in self.strikeOffsets
for i in range(self.numStrikes):
current_offset = sbixHeaderFormatSize + i * sbixStrikeOffsetFormatSize
offset_entry = sbixStrikeOffset()
sstruct.unpack(
sbixStrikeOffsetFormat,
data[current_offset : current_offset + sbixStrikeOffsetFormatSize],
offset_entry,
)
self.strikeOffsets.append(offset_entry.strikeOffset)
# decompile Strikes
for i in range(self.numStrikes - 1, -1, -1):
current_strike = Strike(rawdata=data[self.strikeOffsets[i] :])
data = data[: self.strikeOffsets[i]]
current_strike.decompile(ttFont)
# print " Strike length: %xh" % len(bitmapSetData)
# print "Number of Glyph entries:", len(current_strike.glyphs)
if current_strike.ppem in self.strikes:
from fontTools import ttLib
raise ttLib.TTLibError("Pixel 'ppem' must be unique for each Strike")
self.strikes[current_strike.ppem] = current_strike
# after the glyph data records have been extracted, we don't need the offsets anymore
del self.strikeOffsets
del self.numStrikes
def compile(self, ttFont):
sbixData = b""
self.numStrikes = len(self.strikes)
sbixHeader = sstruct.pack(sbixHeaderFormat, self)
# calculate offset to start of first strike
setOffset = sbixHeaderFormatSize + sbixStrikeOffsetFormatSize * self.numStrikes
for si in sorted(self.strikes.keys()):
current_strike = self.strikes[si]
current_strike.compile(ttFont)
# append offset to this strike to table header
current_strike.strikeOffset = setOffset
sbixHeader += sstruct.pack(sbixStrikeOffsetFormat, current_strike)
setOffset += len(current_strike.data)
sbixData += current_strike.data
return sbixHeader + sbixData
def toXML(self, xmlWriter, ttFont):
xmlWriter.simpletag("version", value=self.version)
xmlWriter.newline()
xmlWriter.simpletag("flags", value=num2binary(self.flags, 16))
xmlWriter.newline()
for i in sorted(self.strikes.keys()):
self.strikes[i].toXML(xmlWriter, ttFont)
def fromXML(self, name, attrs, content, ttFont):
if name == "version":
setattr(self, name, safeEval(attrs["value"]))
elif name == "flags":
setattr(self, name, binary2num(attrs["value"]))
elif name == "strike":
current_strike = Strike()
for element in content:
if isinstance(element, tuple):
name, attrs, content = element
current_strike.fromXML(name, attrs, content, ttFont)
self.strikes[current_strike.ppem] = current_strike
else:
from fontTools import ttLib
raise ttLib.TTLibError("can't handle '%s' element" % name)
# Helper classes
class sbixStrikeOffset(object):
pass
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