src/android/gen_subset_font.py

# -*- coding: utf-8 -*-
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"""Generates subset font.

1. Corrects characters from .svg files in given directory.
  Only text nodes in <text> element are taken into account.
2. Make subset font which contains only the characters corrected above.
"""

import logging
import optparse
import os
import shutil
import subprocess
import sys
import tempfile
from xml.etree import cElementTree as ElementTree

from build_tools import util


def ExtractCharactersFromSvgFile(svg_file):
  result = set()
  for text in ElementTree.parse(svg_file).findall(
      './/{http://www.w3.org/2000/svg}text'):
    if text.text:
      result.update(tuple(text.text))  # Split into characters.
  logging.debug('%s: %s', svg_file, result)
  return result


def ExtractCharactersFromDirectory(svg_paths):
  result = set()
  for dirpath, _, filenames in util.WalkFileContainers(svg_paths):
    for filename in filenames:
      if os.path.splitext(filename)[1] != '.svg':
        # Do nothing for files other than svg.
        continue
      result.update(ExtractCharactersFromSvgFile(
          os.path.join(dirpath, filename)))
  return list(result)


def MakeSubsetFont(fonttools_path, unicodes, input_font, output_font):
  """Makes subset font using fontTools toolchain.

  Args:
    fonttools_path: Path to fontTools library.
    unicodes: A list of unicode characters of which glyph should be in
              the output.
    input_font: Path to input font.
    output_font: Path to output font.
  """
  if not unicodes:
    # subset.py requires at least one unicode character.
    logging.debug('No unicode character is specified. Use "A" as stub.')
    unicodes = [u'A']

  tempdir = tempfile.mkdtemp()
  try:
    # fontTools's output file name is fixed (input file path + '.subset').
    # To get result with specified file name, copy the input font
    # to temporary directory and copy the result with renaming.
    shutil.copy(input_font, tempdir)
    temp_input_font = os.path.join(tempdir, os.path.basename(input_font))
    commands = ['python', os.path.join(fonttools_path, 'subset.py'),
                temp_input_font]
    commands.extend(['U+%08x' % ord(char) for char in unicodes])
    env = os.environ.copy()
    # In fontTools toolchain, "from fontTools import XXXX" is executed.
    # In order for successfull import, add parent directory of the toolchain
    # into PYTHONPATH.
    env['PYTHONPATH'] += ':%s' % os.path.join(fonttools_path, '..')
    if subprocess.call(commands, env=env) != 0:
      sys.exit(1)
    shutil.copyfile('%s.subset' % temp_input_font, output_font)
  finally:
    shutil.rmtree(tempdir)


def ParseOptions():
  """Parses options."""
  parser = optparse.OptionParser()
  parser.add_option('--svg_paths', dest='svg_paths',
                    help='Comma separated paths to a directory or'
                    ' a .zip file containing .svg files.')
  parser.add_option('--input_font', dest='input_font',
                    help='Path to the input font.')
  parser.add_option('--output_font', dest='output_font',
                    help='Path to the output font.')
  parser.add_option('--fonttools_path', dest='fonttools_path',
                    help='Path to fontTools toolchain.')
  parser.add_option('--verbose', dest='verbose',
                    help='Verbosity')
  return parser.parse_args()[0]


def main():
  logging.basicConfig(level=logging.INFO, format='%(levelname)s: %(message)s')

  options = ParseOptions()
  if options.verbose:
    logging.getLogger().setLevel(logging.DEBUG)
  unicodes = ExtractCharactersFromDirectory(options.svg_paths)
  MakeSubsetFont(options.fonttools_path, unicodes,
                 options.input_font, options.output_font)


if __name__ == '__main__':
  main()