fonttools/Lib/fontTools/varLib/interpolate_layout.py

"""
Interpolate OpenType Layout tables (GDEF / GPOS / GSUB).
"""
from __future__ import print_function, division, absolute_import
from fontTools.misc.py23 import *
from fontTools.ttLib import TTFont
from fontTools.varLib import models, VarLibError, load_designspace
from fontTools.varLib.merger import InstancerMerger
import os.path
import logging
from pprint import pformat

log = logging.getLogger("fontTools.varLib.interpolate_layout")


def interpolate_layout(designspace_filename, loc, master_finder=lambda s:s):
	"""
	Interpolate GPOS from a designspace file and location.

	If master_finder is set, it should be a callable that takes master
	filename as found in designspace file and map it to master font
	binary as to be opened (eg. .ttf or .otf).
	"""

	axes, internal_axis_supports, base_idx, normalized_master_locs, masters, instances = load_designspace(designspace_filename)


	log.info("Building interpolated font")
	log.info("Loading master fonts")
	basedir = os.path.dirname(designspace_filename)
	master_ttfs = [master_finder(os.path.join(basedir, m['filename'])) for m in masters]
	master_fonts = [TTFont(ttf_path) for ttf_path in master_ttfs]

	#font = master_fonts[base_idx]
	font = TTFont(master_ttfs[base_idx])

	log.info("Location: %s", pformat(loc))
	loc = {name:axes[name].map_forward(v) for name,v in loc.items()}
	log.info("Internal location: %s", pformat(loc))
	loc = models.normalizeLocation(loc, internal_axis_supports)
	log.info("Normalized location: %s", pformat(loc))

	# Assume single-model for now.
	model = models.VariationModel(normalized_master_locs)
	assert 0 == model.mapping[base_idx]

	merger = InstancerMerger(font, model, loc)

	log.info("Building interpolated tables")
	merger.mergeTables(font, master_fonts, ['GPOS'])
	return font


def main(args=None):
	from fontTools import configLogger

	import sys
	if args is None:
		args = sys.argv[1:]

	designspace_filename = args[0]
	locargs = args[1:]
	outfile = os.path.splitext(designspace_filename)[0] + '-instance.ttf'

	# TODO: allow user to configure logging via command-line options
	configLogger(level="INFO")

	finder = lambda s: s.replace('master_ufo', 'master_ttf_interpolatable').replace('.ufo', '.ttf')

	loc = {}
	for arg in locargs:
		tag,val = arg.split('=')
		loc[tag] = float(val)

	font = interpolate_layout(designspace_filename, loc, finder)
	log.info("Saving font %s", outfile)
	font.save(outfile)


if __name__ == "__main__":
	import sys
	if len(sys.argv) > 1:
		sys.exit(main())
	import doctest
	sys.exit(doctest.testmod().failed)