def subset_truetype(sfnt, character_map, extra_glyphs):
loca = sfnt[b'loca']
glyf = sfnt[b'glyf']
try:
head, maxp = sfnt[b'head'], sfnt[b'maxp']
except KeyError:
raise UnsupportedFont(
'This font does not contain head and/or maxp tables')
loca.load_offsets(head, maxp)
resolved_glyphs = resolve_glyphs(loca, glyf, character_map, extra_glyphs)
if not resolved_glyphs or set(resolved_glyphs) == {0}:
raise NoGlyphs('This font has no glyphs for the specified character '
'set, subsetting it is pointless')
# Keep only character codes that have resolved glyphs
for code, glyph_id in tuple(character_map.iteritems()):
if glyph_id not in resolved_glyphs:
del character_map[code]
# Update the glyf table
glyph_offset_map = glyf.update(resolved_glyphs)
# Update the loca table
loca.subset(glyph_offset_map)
def subset(self, character_map, extra_glyphs):
from calibre.utils.fonts.sfnt.cff.writer import Subset
# Map codes from the cmap table to glyph names, this will be used to
# reconstruct character_map for the subset font
charset_map = {
code: self.cff.charset.safe_lookup(glyph_id)
for code, glyph_id in character_map.iteritems()
}
charset = set(charset_map.itervalues())
charset.discard(None)
if not charset and character_map:
raise NoGlyphs(
'This font has no glyphs for the specified characters')
charset |= {
self.cff.charset.safe_lookup(glyph_id)
for glyph_id in extra_glyphs
}
charset.discard(None)
s = Subset(self.cff, charset)
# Rebuild character_map with the glyph ids from the subset font
character_map.clear()
for code, charname in charset_map.iteritems():
glyph_id = s.charname_map.get(charname, None)
if glyph_id:
character_map[code] = glyph_id
# Check that raw is parseable
CFF(s.raw)
self.raw = s.raw