go-opentype documentation

A pure-Go, zero-dependency TrueType/OpenType text stack. Four small modules that together read a font file, resolve Unicode bidirectional and complex-script text, and rasterise the result — with no golang.org/x/* packages and no cgo anywhere in the stack.

Zero third-party dependencies

Every module in the stack imports only the Go standard library (image, encoding/binary, math, errors, …). That is what lets the whole stack cross-compile trivially to any Go target, including GOOS=js GOARCH=wasm, with no C toolchain and no vendored assets.

The modules

Repo	Module path	What it is
opentype	github.com/go-opentype/opentype	the engine — sfnt parsing + anti-aliased rasterisation
bidi	github.com/go-opentype/bidi	the Unicode Bidirectional Algorithm (UAX #9)
shape	github.com/go-opentype/shape	a HarfBuzz-lite complex-text shaper composing the two above
fonts	github.com/go-opentype/fonts	46 bundled, legible, per-family go:embedded font families
docs	—	this documentation site (MkDocs Material, versioned with mike)
brand	—	logo and brand assets

Each module is standalone and independently importable — shape is the only one that depends on its two siblings; opentype, bidi, and fonts have no intra-org dependencies of their own (fonts depends only on opentype's *Font type for its Parse convenience wrapper).

What it replaces

go-opentype exists to functionally replace, for a Go program that blits glyphs into a pixel buffer:

• the narrow slice of golang.org/x/image/font and font/opentype a glyph-blitting UI needs (parse a font, build a sized face, pull advances and coverage masks), and
• golang.org/x/text/unicode/bidi for laying out mixed left-to-right / right-to-left text.

The stack targets functional parity with the HarfBuzz + FreeType pair, and on the paths it covers, it's there today: TrueType glyf and CFF/CFF2 outline parsing and rasterisation, every GSUB/GPOS lookup type plus GDEF mark filtering, OpenType Variations (fvar/avar/gvar/HVAR/VVAR/ MVAR), a TrueType instruction hinter and a CFF/Type 2 stem grid-fitter, vertical metrics, the OpenType MATH table for math-typesetting metrics (mirroring HarfBuzz's hb-ot-math), the full UAX #9 bidi algorithm through rule L2, and complex-text shaping for Arabic, the Indic scripts, the Universal Shaping Engine (Thai, Lao, Khmer, Myanmar, Tibetan and more), Egyptian Hieroglyph quadrats, Hangul, vertical (CJK tategaki) layout, and Latin/default — see each module's page for its exact support matrix.

Install

go get github.com/go-opentype/opentype
go get github.com/go-opentype/bidi
go get github.com/go-opentype/shape
go get github.com/go-opentype/fonts

Where to go next

• opentype — the sfnt parser and rasteriser: fonts, cmap, TrueType glyf and CFF/CFF2 outlines, variable fonts, GSUB/GPOS shaping, hinting, vertical metrics, the MATH table for math typesetting, font subsetting and descriptor accessors, and the full support matrix.
• bidi — the UAX #9 engine and what it implements vs. defers to a shaper.
• shape — the complex-text shaper: Arabic cursive joining, Indic reordering, the Universal Shaping Engine, Egyptian Hieroglyph quadrats, Hangul, vertical layout, ligatures, mark attachment, kerning, and which scripts it covers.
• fonts — the 46 bundled families and the per-family import model to reach them.
• Guides — task-oriented walkthroughs: rendering text to a PNG, shaping a mixed-direction Arabic string, and picking a bundled font for legibility.

Source lives at github.com/go-opentype.