cffsubr

0.4.0 verified Mon Apr 27 auth: no python

A standalone CFF (Compact Font Format) subroutinizer based on the AFDKO tx tool. It converts CFF fonts to their subroutinized form, reducing file size. Version 0.4.0 requires Python >=3.10. Releases are irregular; maintained by Adobe Type Tools.

pip install cffsubr

Common errors

error AttributeError: module 'cffsubr' has no attribute 'subroutinize' ↓

cause Importing from the wrong path or using an old version where the function was named differently.

fix

Use from cffsubr import subroutinize and ensure cffsubr >= 0.2.0.

error TypeError: subroutinize() missing 1 required positional argument: 'font' ↓

cause Called without passing a TTFont object.

fix

Pass a loaded TTFont instance: subroutinize(font).

error fontTools.ttLib.TTLibError: Unknown font format ↓

cause Input file is not a valid OpenType font (e.g., .ttf, .woff, or corrupt file).

fix

Verify the font is a CFF-based .otf file.

Warnings

breaking In cffsubr 0.4.0, the `subroutinize` function must be called on a TTFont object; it no longer accepts raw bytes or file paths. ↓

fix Use fontTools to load the font first: TTFont('path.otf').

gotcha Only CFF-flavored OpenType fonts (.otf) are supported. TrueType-flavored fonts (.ttf) will not be processed. ↓

fix Ensure the input font has CFF outlines (check with TTFont.sfVersion == 'OTTO').

gotcha The `subroutinize` function modifies the font object in place; it does not return a new font or any status code. ↓

fix After calling, the original font object is modified. Save a copy first if needed.

Imports

subroutinize

wrong

from cffsubr.cffsubr import subroutinize

correct

from cffsubr import subroutinize

cffsubr is a single module; no submodule.

Quickstart

Load a CFF font, subroutinize it, and save.

from cffsubr import subroutinize
from fontTools.ttLib import TTFont

font = TTFont('input.otf')
subroutinize(font)
font.save('output.otf')