fontmask
Patch a font with the secret-masking rules from Obel Mono Masked.
fontmask copies the ccmp rule set from the bundled Obel font, maps its
glyphs to the target through Unicode, adds note glyphs that copy the target's
own outlines, and adds the mask dots. The output family is <Family> Masked.
The mask is visual only. Copy and paste still returns the real text.
Install
With Nix:
nix develop
uv sync --extra test
From PyPI:
uvx fontmask inspect Font.ttf
uvx --from 'fontmask==0.1.0' fontmask inspect Font.ttf
From a git tag:
uvx git+https://github.com/mattrobenolt/fontmask@v0.1.0 inspect Font.ttf
uvx git+https://github.com/mattrobenolt/fontmask@v0.1.0 patch Font.ttf -o FontMasked.ttf
The PyPI commands use the latest release. The git commands pin the v0.1.0 tag.
Use
fontmask inspect Font.ttf
fontmask patch Font.ttf -o FontMasked.ttf
fontmask patch Variable.ttf --instance wght=400 -o VariableMasked.ttf
patch --dry-run prints the plan and writes no file.
Turn it on
Install the output font and select <Family> Masked in the app. The masking is
always on; there is no separate switch.
| App | Setting |
|---|---|
| Terminal.app | Settings → Profiles → Text → Font → Change → <Family> Masked |
| iTerm2 | Settings → Profiles → Text → Font → <Family> Masked, then enable Use ligatures |
| VS Code | "editor.fontFamily": "<Family> Masked" and "editor.fontLigatures": true |
| Zed | "buffer_font_family": "<Family> Masked" |
| Ghostty | font-family = "<Family> Masked" |
| Kitty | font_family <Family> Masked |
| WezTerm | font = wezterm.font("<Family> Masked") |
| Windows Terminal | Settings → Profiles → Appearance → Font face → <Family> Masked |
Apps that do not shape text, like Alacritty, show the plain string.
Supported fonts
TrueType, CFF, WOFF/WOFF2, static and variable fonts, proportional fonts, fonts with no GSUB, and TTC collections. CFF2 variable output is not supported. Variable fonts are instanced to a static font. Proportional fonts get one mask glyph per advance width, so the line width does not change.
How it works
Obel Mono keeps the rules in ccmp. fontmask copies the 108-lookup closure,
maps its glyph names to the target, adds the note and mask glyphs, and appends
the lookups to the target's GSUB table. tests/test_patch.py shapes 520
strings in both fonts and compares the output.
Limits
- The mask changes pixels only. It does not change the text buffer.
- Mask glyphs are unencoded. The tool does not add cmap entries.
- Color fonts are not supported. Mask glyphs render as monochrome outlines.
- Check the target font's license before distributing the patched font.
Development
nix develop, then uv sync --extra test, uv check, and uv run pytest -q.
Credit
The rules and the mask dot are from Obel Mono by Cody Collier and the Obel Mono Project Authors. Read the original post, A typeface that keeps a secret.
License
The tool is MIT. The bundled rules font is SIL OFL 1.1; see
src/fontmask/data/OFL.txt. The patched font is a derivative of the target and
the Obel material. Check the target's license before distribution.
1 maintainer
Metadata
1 maintainer
Release files for fontmask 0.1.0
For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.
Source distribution (sdist)
| File | Size | Uploaded | Provenance | Actions |
|---|---|---|---|---|
| fontmask-0.1.0.tar.gz | 151.7 kB | With provenance | Details for fontmask-0.1.0.tar.gz |
Built distribution (wheel)
| File | Interpreter | ABI | Platform | Actions Reset |
|---|---|---|---|---|
| fontmask-0.1.0-py3-none-any.whl | Python 3 | none | any | Details for fontmask-0.1.0-py3-none-any.whl |
Total release size: 306.9 kB
Release files / fontmask-0.1.0.tar.gz
| Download URL | fontmask-0.1.0.tar.gz |
|---|---|
| Size | 151.7 kB |
| Tags | Source |
|
SHA-256 checksum How to use checksums |
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| Download URL | fontmask-0.1.0-py3-none-any.whl |
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| Size | 155.2 kB |
| Tags | Python 3 |
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| Uploaded via |
uv/0.13.7 {"installer":{"name":"uv","version":"0.13.7","subcommand":["publish"]},"python":null,"implementation":{"name":null,"version":null},"distro":{"name":"Ubuntu","version":"24.04","id":"noble","libc":null},"system":{"name":null,"release":null},"cpu":null,"openssl_version":null,"setuptools_version":null,"rustc_version":null,"ci":true}
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