Prune unused lookups from GPOS and GSUB tables

prune_unused_lookups.py

"""Use FontTools subsetter's prune_lookup method to remove all unreferenced lookups from GPOS and GSUB tables."""

import sys
from fontTools.misc.cliTools import makeOutputFileName
from fontTools.ttLib import TTFont

# importing this dynamically adds a prune_lookups method to GPOS/GSUB classes
from fontTools import subset

input_file = sys.argv[1]
font = TTFont(input_file)

for table_tag in ("GPOS", "GSUB"):
    if table_tag not in font:
        continue
    font[table_tag].prune_lookups(remap=True)

# save the modified font to <input_file>#1.ttf, #2, etc. to avoid overwriting original
font.save(makeOutputFileName(input_file))