Converts a Type 1 font into a OpenType-CFF font

convert_type1_to_opentype-cff.py

# Copyright 2023 Adobe, Inc. All Rights Reserved.
# Author: Miguel Sousa

"""
Converts a Type 1 font into a OpenType-CFF font.
"""
import argparse
from fontTools.agl import toUnicode
from fontTools.fontBuilder import FontBuilder
from fontTools.misc.cliTools import makeOutputFileName
from fontTools.pens.basePen import NullPen
from fontTools.pens.t2CharStringPen import T2CharStringPen
from fontTools.t1Lib import T1Font


def convert_font(input_path):
    t1 = T1Font(input_path)
    t1.parse()

    # Collect 'name' table strings
    font_name = t1.font.get('FontName', '')
    font_info = t1.font.get('FontInfo', {})
    full_name = font_info.get('FullName', '')
    font_version = font_info.get('version', '')
    name_strings = dict(
        familyName=font_info.get('FamilyName', ''),
        styleName=font_info.get('Weight', ''),
        fullName=full_name,
        psName=font_name,
        version=f"Version {font_version}",
        uniqueFontIdentifier=f"{font_version};{font_name}",
    )

    # Collect glyph names
    encoding = t1.font.get('Encoding')
    char_names = t1.font.get('CharStrings')
    gnames = []
    for gname in encoding:
        if gname not in gnames:
            gnames.append(gname)

    for gname in char_names:
        if gname not in gnames:
            gnames.append(gname)

    # Infer 'cmap' table values from glyph names
    cmap = {}
    for gname in gnames:
        char = toUnicode(gname)
        if char:
            cmap[ord(char)] = gname

    # Collect charstrings and advance widths
    char_strings = {}
    adv_widths = {}
    gset = t1.getGlyphSet()
    npen = NullPen()

    for gname in gnames:
        glyph = gset[gname]
        glyph.draw(npen)
        gwidth = round(glyph.width)
        adv_widths[gname] = gwidth
        t2pen = T2CharStringPen(gwidth, None)
        glyph.draw(t2pen)
        cs = t2pen.getCharString()
        char_strings[gname] = cs

    fb = FontBuilder(1000, isTTF=False)
    fb.setupGlyphOrder(gnames)
    fb.setupCharacterMap(cmap)
    fb.setupCFF(font_name, {"FullName": full_name}, char_strings, {})

    lsb = {}
    for gname, cs in char_strings.items():
        xmin = 0
        gbbox = cs.calcBounds(None)
        if gbbox:
            xmin, *_ = gbbox
        lsb[gname] = xmin

    metrics = {
        gname: (adv_width, lsb[gname])
        for gname, adv_width in adv_widths.items()
    }

    fb.setupHorizontalMetrics(metrics)
    fb.setupHorizontalHeader(ascent=824, descent=-200)
    fb.setupNameTable(name_strings, mac=False)
    fb.setupOS2(sTypoAscender=824, usWinAscent=824, usWinDescent=200)
    fb.setupPost()
    save_path = makeOutputFileName(input_path, extension='.otf')
    fb.save(save_path)


def main(args=None):
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('input_path', help='path to Type 1 font file')
    opts = parser.parse_args(args)

    convert_font(opts.input_path)


if __name__ == "__main__":
    main()