#ttf #truetype #opentype

ttf-parser

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

2 unstable releases

✓ Uses Rust 2018 edition

0.2.0 Jul 10, 2019
0.1.0 Jun 18, 2019

#51 in Parser implementations

Download history 36/week @ 2019-06-12 187/week @ 2019-06-19 53/week @ 2019-06-26 75/week @ 2019-07-03

122 downloads per month
Used in 3 crates (1 directly)

MIT/Apache

153KB
3.5K SLoC

ttf-parser

Build Status Crates.io Documentation

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

Features

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

Supported TrueType features

Supported OpenType features

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 40% more time to outline all glyphs in SourceSansPro-Regular.otf (which uses CFF) rather than in SourceSansPro-Regular.ttf.

test outline_cff  ... bench:   1,651,557 ns/iter (+/- 2,751)
test outline_glyf ... bench:     977,046 ns/iter (+/- 4,973)

Here is some methods benchmarks:

test outline_glyph_276_from_cff  ... bench:       1,247 ns/iter (+/- 2)
test outline_glyph_276_from_glyf ... bench:         817 ns/iter (+/- 15)
test outline_glyph_8_from_cff    ... bench:         521 ns/iter (+/- 2)
test family_name                 ... bench:         445 ns/iter (+/- 4)
test from_data_otf               ... bench:         435 ns/iter (+/- 1)
test outline_glyph_8_from_glyf   ... bench:         360 ns/iter (+/- 7)
test from_data_ttf               ... bench:         133 ns/iter (+/- 0)

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

test glyph_index_u41     ... bench:      24,648 ns/iter (+/- 256)
test glyph_2_hor_metrics ... bench:       8,421 ns/iter (+/- 18)
test units_per_em        ... bench:         564 ns/iter (+/- 2)
test x_height            ... bench:         568 ns/iter (+/- 1)
test strikeout_metrics   ... bench:         564 ns/iter (+/- 0)
test width               ... bench:         422 ns/iter (+/- 0)
test ascender            ... bench:         279 ns/iter (+/- 1)
test subscript_metrics   ... bench:         279 ns/iter (+/- 0)

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

Safety

  • The library must not panic. Any panic considered as a critical bug and should be reported.
  • The library forbids unsafe code.

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.

License

Licensed under either of

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.

No runtime deps