Python script to vertically center glyphs in a font

vert-center-glyphs.py

# Python script to vertically center a set of glyphs in a font.
# Requires fontforge python module.
# Credits to u/janKeTami here: https://www.reddit.com/r/FontForge/comments/11r6x4q/vertically_centering_glyphs/
# Slightly altered to enable this script to be run straight from the terminal using ttf/otf fonts

import re
import os
import argparse
try:
    import psMat
    import fontforge
except ImportError:
    sys.exit("FontForge module not found")

folder = "patched"
try:
    os.makedirs(folder)
except FileExistsError:
    pass

parser = argparse.ArgumentParser(description="Vertically center glyphs in a font.")
parser.add_argument("file", help="Filename of font to be patched")
args = parser.parse_args()

# Change the start and end glyph to those you desire
# Example provided below is for 126, corresponding to tilde
startglyph = 126
endglyph = 126

thisfont = fontforge.open(args.file)
for i in range(startglyph,endglyph+1):
    ytop = thisfont[i].boundingBox()[-1] # counted from baseline, excluding descent!
    ybot = thisfont[i].boundingBox()[1] # same note as above
    # Calculation method:
    # Midpoint of entire space = (ascent + descent) / 2
    # Current midpoint of glyph (counted from baseline) = (ytop + ybot) / 2
    # Current midpoint of glyph (counted with descent) = (ytop + ybot) / 2 + descent
    # Vertical translation = midpoint of entire space - current midpoint of glyph (counted with descent)
    # That is: (ascent + descent) / 2 - ((ytop + ybot) / 2 + descent)
    # Simplified: (ascent - descent - (ytop + ybot)) / 2 
    translation = (thisfont.ascent - thisfont.descent - (ytop + ybot)) / 2
    thisfont[i].transform( psMat.translate( 0, translation ))

# This bit for flags and bitmaps is taken from Nerd Fonts' font-patcher script
# No idea if this is necessary, but just in case
if int(fontforge.version()) >= 20201107:
    gen_flags = (str('opentype'), str('no-FFTM-table'))
else:
    gen_flags = (str('opentype'))

bitmaps = str()
if len(thisfont.bitmapSizes):
    print("Preserving bitmaps {}".format(thisfont.bitmapSizes))
    bitmaps = str('otf') # otf/ttf, both is bf_ttf

splitfilename = args.file.rsplit('/', 1)
if len(splitfilename) > 1:
    filename = splitfilename[1]
else:
    filename = args.file
outfont = folder + "/" + filename
thisfont.generate(outfont, bitmap_type=bitmaps, flags=gen_flags)
print("Font patched successfully! Stored at {}".format(outfont))