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_backend_pdf_ps.py
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189 lines (156 loc) · 5.83 KB
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"""
Common functionality between the PDF and PS backends.
"""
from io import BytesIO
import functools
import logging
from fontTools import subset
import matplotlib as mpl
from .. import font_manager, ft2font
from .._afm import AFM
from ..backend_bases import RendererBase
@functools.lru_cache(50)
def _cached_get_afm_from_fname(fname):
with open(fname, "rb") as fh:
return AFM(fh)
def get_glyphs_subset(fontfile, characters):
"""
Subset a TTF font
Reads the named fontfile and restricts the font to the characters.
Parameters
----------
fontfile : str
Path to the font file
characters : str
Continuous set of characters to include in subset
Returns
-------
fontTools.ttLib.ttFont.TTFont
An open font object representing the subset, which needs to
be closed by the caller.
"""
options = subset.Options(glyph_names=True, recommended_glyphs=True)
# Prevent subsetting extra tables.
options.drop_tables += [
'FFTM', # FontForge Timestamp.
'PfEd', # FontForge personal table.
'BDF', # X11 BDF header.
'meta', # Metadata stores design/supported languages (meaningless for subsets).
'MERG', # Merge Table.
'TSIV', # Microsoft Visual TrueType extension.
'Zapf', # Information about the individual glyphs in the font.
'bdat', # The bitmap data table.
'bloc', # The bitmap location table.
'cidg', # CID to Glyph ID table (Apple Advanced Typography).
'fdsc', # The font descriptors table.
'feat', # Feature name table (Apple Advanced Typography).
'fmtx', # The Font Metrics Table.
'fond', # Data-fork font information (Apple Advanced Typography).
'just', # The justification table (Apple Advanced Typography).
'kerx', # An extended kerning table (Apple Advanced Typography).
'ltag', # Language Tag.
'morx', # Extended Glyph Metamorphosis Table.
'trak', # Tracking table.
'xref', # The cross-reference table (some Apple font tooling information).
]
# if fontfile is a ttc, specify font number
if fontfile.endswith(".ttc"):
options.font_number = 0
font = subset.load_font(fontfile, options)
subsetter = subset.Subsetter(options=options)
subsetter.populate(text=characters)
subsetter.subset(font)
return font
def font_as_file(font):
"""
Convert a TTFont object into a file-like object.
Parameters
----------
font : fontTools.ttLib.ttFont.TTFont
A font object
Returns
-------
BytesIO
A file object with the font saved into it
"""
fh = BytesIO()
font.save(fh, reorderTables=False)
return fh
class CharacterTracker:
"""
Helper for font subsetting by the pdf and ps backends.
Maintains a mapping of font paths to the set of character codepoints that
are being used from that font.
"""
def __init__(self):
self.used = {}
def track(self, font, s):
"""Record that string *s* is being typeset using font *font*."""
char_to_font = font._get_fontmap(s)
for _c, _f in char_to_font.items():
self.used.setdefault(_f.fname, set()).add(ord(_c))
def track_glyph(self, font, glyph):
"""Record that codepoint *glyph* is being typeset using font *font*."""
self.used.setdefault(font.fname, set()).add(glyph)
class RendererPDFPSBase(RendererBase):
# The following attributes must be defined by the subclasses:
# - _afm_font_dir
# - _use_afm_rc_name
def __init__(self, width, height):
super().__init__()
self.width = width
self.height = height
def flipy(self):
# docstring inherited
return False # y increases from bottom to top.
def option_scale_image(self):
# docstring inherited
return True # PDF and PS support arbitrary image scaling.
def option_image_nocomposite(self):
# docstring inherited
# Decide whether to composite image based on rcParam value.
return not mpl.rcParams["image.composite_image"]
def get_canvas_width_height(self):
# docstring inherited
return self.width * 72.0, self.height * 72.0
def get_text_width_height_descent(self, s, prop, ismath):
# docstring inherited
if ismath == "TeX":
return super().get_text_width_height_descent(s, prop, ismath)
elif ismath:
parse = self._text2path.mathtext_parser.parse(s, 72, prop)
return parse.width, parse.height, parse.depth
elif mpl.rcParams[self._use_afm_rc_name]:
font = self._get_font_afm(prop)
l, b, w, h, d = font.get_str_bbox_and_descent(s)
scale = prop.get_size_in_points() / 1000
w *= scale
h *= scale
d *= scale
return w, h, d
else:
font = self._get_font_ttf(prop)
font.set_text(s, 0.0, flags=ft2font.LoadFlags.NO_HINTING)
w, h = font.get_width_height()
d = font.get_descent()
scale = 1 / 64
w *= scale
h *= scale
d *= scale
return w, h, d
def _get_font_afm(self, prop):
fname = font_manager.findfont(
prop, fontext="afm", directory=self._afm_font_dir)
return _cached_get_afm_from_fname(fname)
def _get_font_ttf(self, prop):
fnames = font_manager.fontManager._find_fonts_by_props(prop)
try:
font = font_manager.get_font(fnames)
font.clear()
font.set_size(prop.get_size_in_points(), 72)
return font
except RuntimeError:
logging.getLogger(__name__).warning(
"The PostScript/PDF backend does not currently "
"support the selected font (%s).", fnames)
raise