Downsizing an .OTF font by removing glyphs

Question

I can't quite believe this question hasn't been asked specifically for OpenType fonts, but does anyone know of a way to remove glyphs from these fonts?

I have an .OTF with a very large file-size (almost 10MB) and I need to make it smaller. The reasons are two fold.

1) I'm trying to prepare it for web embedding, so the smaller the files, the easier for the client.

2) Font Squirrel (used for easy preparation of font files) has a 2MB upload limit - I know there are alternatives, but none so far have been successful. To save wasting peoples time, the ones I've tried that have failed are http://fontface.codeandmore.com/ and http://www.font2web.com/. CodeAndMore.com appears to work, but the fonts it spits back out are completely different to the one I gave it.

Please be aware I'm not a font expert, so go easy on the answer.

Answer 1

I've written a Python2 script with fontforge library does the following:

• Accepts a source font
• Accepts a file containing all characters to be used. It can be a translation file, string asset file, HTML file, etc.
• Output a font with characters that aren't shown in the file removed

Here is the code:

#!/usr/bin/python2
import sys
import fontforge

if len(sys.argv) == 4:
    font = fontforge.open(sys.argv[1])

    with open(sys.argv[2], "r") as f:
        for i in f.read().decode("UTF-8"):
            font.selection[ord(i)] = True

    font.selection.invert()

    for i in font.selection.byGlyphs:
        font.removeGlyph(i)

    font.generate(sys.argv[3])
else:
    print "WARNING: Check the license of the source font\nbefore distributing the output font generated by this script.\nI'm not responsible for any legal issue caused by\ninappropriate use of this script!\n"
    print "Usage: {} [source font] [file with glyphs NOT to be removed] [output]".format(sys.argv[0])
    print "Example: {} /path/to/ukai.ttc chineseTranslation.txt ukaiStripped.ttf".format(sys.argv[0])

Please notice that it may not be legal to use this script on certain fonts. Ensure to checkout the license of the source font. I'm not responsible for any legal issue caused by using any font generated by this script.

Answer 2

FontTools has a program called pyftsubset that does it

https://github.com/behdad/fonttools

Usage something like this:

pyftsubset MyFont.otf --output-file=MyFontStripped.otf --unicodes-file=file-of-codes.txt

Where file-of-codes.txt contains a list of codes like:

U+09c78
U+09ce5
U+09ce7
U+09ce9
U+09ceb
U+09cec
U+09cf0
U+09cf3
U+09cf4
U+09cf6
...

Answer 3

Following latest comment: You can select several sets at a time in the left menu (Languages) using shift and command key all in one shot. Note the image keeps the Basic Latin (A-Z a-z). Once you have the sets selected click in the glyphs window and Select All (cmd-A). It will take some time if there are a lot as this case. Then cmd-Delete and you remove all. You only need to repeat the operation with 'Categories' and you're done. Then export .otf

Answer 4

Ran into this today because I was trying to save a font after CTRL+A and setting width (don't do that, btw). I went with a little more straight-forward Python scripting approach since I already had the font open in FontForge.

This assumes that you have the intended font open and have it active. It also supposes that you only want to keep the first 128 characters (ASCII range). It selects everything then uses the "less" flag to deselect the range from 0-127. Have a look at the FontForge Python scripting guide for some more info on the different ways you can manipulate the selection.

File > Execute Script

font = fontforge.activeFont()
font.selection.all()
font.selection.select(("ranges","less"),0,127)
font.clear()

Answer 5

A 10 MB Opentype font is very rare because it's very heavy weight, so I assume it's an in-house specific font and not commercial. For removing glyphs you can edit the font in FontForge (free) or any other commercial font editor and after that regenerate the .otf (also .ttf)

For building webfonts (I guess you'll need .ttf, .svg, .eot and .woff) you can use locally several free tools: sfnt2woff, ttf2eot, Batik SVG and with ttfautohint you can improve the way the font will look in the screen before making the conversion.

Answer 6

As pointed out by others, you can use fonttools to remove unwanted glyphs from a font.

Installation is straightforward with pip:

pip install fonttools

You can then use pyftsubset function to restrict a font to a subset of characters. For instance if you want to keep only basic latin characters (punctuation, digits, letters):

pyftsubset myFont.otf --output-file=mySmallerFont.otf --unicodes=U+0020-007E

You can also convert the font at the same time:

pyftsubset myFont.otf --output-file=mySmallerFont.woff --flavor=woff --unicodes=U+0020-007E

Note that if you need to convert to woff2, you will have to install brotli first, using pip install brotli.

Full documentation is available here.

Answer 7

fonttools has now been adopted by Google: https://github.com/googlei18n/fonttools. I've been using it to reduce the number of glyphs in Google's Noto fonts for use in an embedded system. Works a treat!

Answer 8

@remeus's answer inspired me, but I don't want to use the pyftsubset.exe^{fontTools.subset} directly; I want to use the script since I can easily add something to it.

CODE

import fontTools.subset
from pathlib import Path
import os

SOURCE_FILE = Path('YOUR.ttf') # ttf, otf, ...
OUT_FORMAT = 'woff' # otf, woff, woff2, ...
TEXT_FILE = Path('YOUR.txt')

def main():
    output_file = Path('temp') / Path(SOURCE_FILE.stem + '.' + OUT_FORMAT)
    output_file.parent.mkdir(parents=True, exist_ok=True)
    args = [SOURCE_FILE,
            f"--output-file={output_file}",
            # f"--text=中英文 abcdefg",
            f"--text-file={TEXT_FILE}",  # 中英文 abcdefg
            # "--unicodes=U+0020-007E",
            f"--flavor={OUT_FORMAT}",
            #  https://github.com/fonttools/fonttools/blob/1df4f1e/Lib/fontTools/subset/__init__.py#L332-L337
            "--verbose=true", # https://github.com/fonttools/fonttools/blob/1df4f1e/Lib/fontTools/subset/__init__.py#L3015
            # "--xml=true",
            "--timing=true",
            ]
    fontTools.subset.main([str(_) for _ in args])
    os.startfile(output_file.parent)


if __name__ == "__main__":
    main()

Explain

Here are three ways to specify the subset you want

1. --text: Write directly

2. --text-file: Write the text in the file (It doesn't matter if you repeat it, the code will automatically remove it for you) (I recommend this way.)

   example:

   my.txt (utf-8)

   0123456
   abcdefg
   ABCDEFG
   中英文
   

3. --unicodes: Use unicode range

If you need to convert to woff2, you will have to install brotli first, using pip install brotlicffi.

resason:

• haveBrotli (it will try import brotlicffi first, so I recommand pip install brotlicffi not brotli)
• ImportError("No module named brotli")

Other issue

Below is indirect issues. You can directly skip this paragraph if you don't want to see it.

Here is my experience, I want to use the font on the browser, but I get an error as below

OTS parsing error: Web font size more than 30MB

my font-size

• size: 40MB
• format: ttf

So, If I change the format to Woff or Woff2 may solve the problem.

Still, you can use fontTools again

TTFont(Path()).save(Path())

It cost too much time when your file size is large.

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