ufo-tdkit-tools

PS hints extraction, optimization, and preserve-mode compilation for UFO fonts.

Features

• extraction -- Convert binary fonts (OTF/TTF/WOFF/WOFF2) to UFO with full PS hint preservation (multi-entry hintSetList, counter triplets hstem3/vstem3, font-level Private dict including StdHW/StdVW) and FEA post-processing (one feature block per tag, inlined aalt for spec compliance).
• ps_hints -- Parse, optimize, analyze, and validate PostScript hints in UFO fonts; move hints between processedglyphs / glyph lib / default layers.
• compilation -- Compile UFO back to OTF preserving PS hints (via AFDKO makeotf + per-glyph charstring merge, then production glyph names + cffsubr subroutinization). Parallel batch via ProcessPoolExecutor.

Installation

pip install ufo-tdkit-tools                    # core (constants, ps_hints parser)
pip install ufo-tdkit-tools[extraction]        # + binary font conversion
pip install ufo-tdkit-tools[compilation]       # + OTF compilation with hints
pip install ufo-tdkit-tools[all]               # everything

The extraction and compilation extras pull in AFDKO (>=5,<6), whose wheels ship the tx and makeotf executables the compiler runs — nothing needs to be installed separately.

Quick start

The simplest path is the process_font pipeline — any input (binary or UFO, hinted or not) becomes a hinted OTF + a clean UFO:

from ufo_tdkit_tools import process_font

result = process_font(
    "input.otf",          # OTF / TTF / WOFF / WOFF2 / UFO
    "out.otf",
    "out.ufo",
    hint_source="auto",   # priority: processed > v2 > public_ps
    autohint="fill",      # "fill" | "all" | "off"
    optimize=False,       # set True to run the ps_hints optimizer
)
assert result.success
print(result.glyphs_with_hints, "/", result.glyphs_total,
      "autohinted=", result.autohinted_count,
      "in otf=", result.otf_glyphs_hinted)

Glyphs the chosen source does not hint are autohinted individually with afdko.otfautohint — a partially hinted master (base forms hinted, composites not) comes out fully hinted, with the authored hints kept. autohint="all" re-hints everything instead, autohint="off" leaves the gaps alone.

For the lower-level entry points (extraction.convert_binary_to_ufo, compilation.compile_otf_preserve_optimized, the ps_hints parser / optimizer / validator / batch wrappers), see docs/API.md.

Legacy kern table for Word

Modern build tools emit kerning only as GPOS, which Microsoft Word ignores. add_legacy_kern regenerates the old-style kern table from the font's own GPOS kern feature, rewriting the binary so that nothing but kern changes:

from ufo_tdkit_tools import add_legacy_kern

pairs = add_legacy_kern("Sans-Regular.ttf")   # 0 if the font has no GPOS kerning

It needs only fontTools — no extras required.

Command line

Installing the package (uv sync / pip install) provides the ufo-tdkit-tools console script (also runnable as python -m ufo_tdkit_tools). It wraps process_font for batch builds:

# Re-hint/optimize a batch of OTFs in place (temp UFO created & discarded)
ufo-tdkit-tools optimize-otf --in-place *.otf

# Or write fresh <stem>.otf + <stem>.ufo pairs into a directory
ufo-tdkit-tools optimize-otf -o build/ Sans-Regular.otf Sans-Bold.otf

# Skip the ps_hints optimizer (autohint + compile only)
ufo-tdkit-tools optimize-otf --in-place --no-optimize *.otf

# Keep only the authored hints, never call the autohinter
ufo-tdkit-tools optimize-otf -o build/ --autohint off Src.ufo

Every run prints one machine-parseable summary line and exits non-zero if any input failed — convenient inside a build log:

optimized=36 autohinted=0 failed=0

--in-place only rewrites .otf inputs (atomically, so a mid-pipeline failure never corrupts the source). UFO and other binary inputs use -o DIR.

Round-trip fidelity

OTF → UFO → OTF preserves declared hstem/vstem positions and widths byte-for-byte, hint substitution between drawing operations, counter-mask grouping, and font-level Private dict scalars. The one structural exception is hint substitution that fires between subpaths (a hintmask immediately before a moveto, common on disconnected glyphs like i, j, dieresis-bearing letters): the autohint.v2 format has no anchor for these and AFDKO's own autohint produces the same flattening.

Metadata (OS/2, head, name) also round-trips: fsType, weight/width class, vendor ID, Unicode/code-page ranges, PANOSE, typo/win/hhea metrics, sub/superscript and strikeout, head.macStyle/head.flags, and all name records. The OS/2.fsSelection flags USE_TYPO_METRICS (bit 7), WWS (bit 8) and OBLIQUE (bit 9) are restored during extraction — ufo-extractor (≤ 0.8.1) drops them, so they are re-read straight from the source OS/2 table.

License

Apache-2.0