ttf-parser

A high-level, safe, zero-allocation TrueType font parser.

Features

• A high-level API.
• Zero allocations.
• Zero dependencies.
• no_std compatible.
• Fast.
• Stateless.
• Simple and maintainable code (no magic numbers).

Supported TrueType features

• (cmap) Character to glyph index mapping using [glyph_index()] method.
  All subtable formats except Mixed Coverage (8) are supported.
• (cmap) Character variation to glyph index mapping using [glyphvariationindex()] method.
• (glyf) Glyph outlining using [outline_glyph()] method.
• (hmtx) Retrieving a glyph's horizontal metrics using [glyphhormetrics()] method.
• (vmtx) Retrieving a glyph's vertical metrics using [glyphvermetrics()] method.
• (kern) Retrieving a glyphs pair kerning using [glyphs_kerning()] method.
• (maxp) Retrieving a total number of glyphs using [numberofglyphs()] method.
• (name) Listing all name records using [names()] method.
• (name) Retrieving a font's family name using [family_name()] method.
• (name) Retrieving a font's PostScript name using [postscriptname()] method.
• (post) Retrieving a font's underline metrics name using [underline_metrics()] method.
• (head) Retrieving a font's units per EM value using [unitsperem()] method.
• (hhea) Retrieving a generic font info using: [ascender()], [descender()], [height()] and [line_gap()] methods.

Supported OpenType features

• (CFF) Glyph outlining using [outline_glyph()] method.
• (OS/2) Retrieving a font kind using [isregular()], [isitalic()], [isbold()] and [isoblique()] methods.
• (OS/2) Retrieving a font's weight using [weight()] method.
• (OS/2) Retrieving a font's width using [width()] method.
• (OS/2) Retrieving a font's X height using [x_height()] method.
• (OS/2) Retrieving a font's strikeout metrics using [strikeout_metrics()] method.
• (OS/2) Retrieving a font's subscript metrics using [subscript_metrics()] method.
• (OS/2) Retrieving a font's superscript metrics using [superscript_metrics()] method.

Methods' computational complexity

TrueType fonts designed for fast querying, so most of the methods are very fast. The main exception is glyph outlining. Glyphs can be stored using two different methods: using Glyph Data format and Compact Font Format (pdf). The first one is fairly simple which makes it faster to process. The second one is basically a tiny language with a stack-based VM, which makes it way harder to process. Currently, it takes 60% more time to outline all glyphs in SourceSansPro-Regular.otf (which uses CFF) rather than in SourceSansPro-Regular.ttf.

test outline_cff ... bench: 1,617,138 ns/iter (+/- 1,261) test outline_glyf ... bench: 995,771 ns/iter (+/- 2,801)

Here is some methods benchmarks:

test outline_glyph_276_from_cff ... bench: 1,203 ns/iter (+/- 4) test outline_glyph_276_from_glyf ... bench: 796 ns/iter (+/- 3) test outline_glyph_8_from_cff ... bench: 497 ns/iter (+/- 3) test from_data_otf ... bench: 372 ns/iter (+/- 5) test outline_glyph_8_from_glyf ... bench: 347 ns/iter (+/- 1) test family_name ... bench: 269 ns/iter (+/- 3) test from_data_ttf ... bench: 72 ns/iter (+/- 3) test glyph_index_u41 ... bench: 24 ns/iter (+/- 0) test glyph_2_hor_metrics ... bench: 8 ns/iter (+/- 0)

family_name is expensive, because it allocates a String and the original data is stored as UTF-16 BE.

Some methods are too fast, so we execute them 1000 times to get better measurements.

test x_height ... bench: 847 ns/iter (+/- 0) test units_per_em ... bench: 564 ns/iter (+/- 2) test strikeout_metrics ... bench: 564 ns/iter (+/- 0) test width ... bench: 287 ns/iter (+/- 0) test ascender ... bench: 279 ns/iter (+/- 1) test subscript_metrics ... bench: 279 ns/iter (+/- 0)

Safety

• The library must not panic. Any panic considered as a critical bug and should be reported.
• The library has a single unsafe block for array casting.

Alternatives

• font-rs - Mainly a glyph outline extractor. No documentation. Has less features. Doesn't support CFF. Has a lot of magic numbers.
• stb_truetype - Mainly a glyph outline extractor. Isn't allocation free. Has less features. Doesn't support CFF. Has a lot of magic numbers. Uses panic a lot.
• truetype - Simply maps TrueType data to the Rust structures. Doesn't actually parses the data. Isn't allocation free. Has some unsafe. Unmaintained.
• font - Very similar to ttf-parser, but supports less features. Still an alpha. Isn't allocation free.
• fontdue - Parser and rasterizer. In alpha state. Allocates all the required data. Doesn't support CFF.

(revised on 2019-09-24)

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.