tpt-colour

A pure-Rust colour management substrate: colour spaces and maths, alpha compositing, ICC profile parsing and transforms, and gamut mapping.

It is no_std throughout (the ICC crate also needs alloc). The scalar path is the reference. SIMD batching is optional behind the simd feature, which uses tpt-simd (pinned to a commit). It produces bit-identical output and needs Rust 1.95; the default build keeps the 1.85 MSRV.

Crates

Each crate has its own README, changelog and examples.

Crate	Purpose	Docs
tpt-colour	Facade crate that re-exports the others. Start here.	README · examples
tpt-colour-core	Colour spaces (sRGB, P3, Rec. 2020, Adobe RGB, Lab, Oklab, YCbCr), HSL/HSV/HWB/xyY, ΔE formulas, WCAG and APCA contrast, palettes, colour-vision simulation, and Porter-Duff / blend compositing	README · examples
tpt-colour-icc	ICC profiles (v2/v4): matrix/TRC and LUT (mft1, mft2, mAB , mBA ) transforms, writing, black point compensation, absolute colorimetric	README · examples
tpt-colour-manage	Gamut boundaries, CSS Colour 4 OKLCH gamut mapping, ColourManager with transform caching, soft proofing, HDR tone mapping (PQ, HLG, Reinhard)	README · examples

Tools and bindings, not published: tpt-colour-cli (the tpt-colour command), tpt-colour-wasm, tpt-colour-capi and tpt-colour-py. tpt-colour-oracle compares output against LittleCMS. It is excluded from the workspace and never shipped.

Quick start

use tpt_colour::ColourManager;
use tpt_colour::icc::RenderingIntent;

let mut colour = ColourManager::new(); // registers "srgb" and "display-p3"
colour.register_icc("fogra39", &std::fs::read("FOGRA39.icc")?)?;

let to_print = colour.transform("srgb", "fogra39", RenderingIntent::Perceptual)?;
let cmyk = to_print.transform_rgb([0.8, 0.2, 0.1])?;

Run the example with cargo run -p tpt-colour --example convert. The crate README lists all the examples, and the mdBook guide explains the design choices behind them.

Principles

• Pure Rust in shipped crates. No C-FFI or -sys crates. cargo deny enforces this.
• Deterministic maths. Operations keep a fixed order, avoid FMA, and use libm rather than platform std maths, so results match bit-for-bit across targets.
• Precision. Bulk transforms use f32 with curves baked into 4096-point tables, which is accurate to about 2e-5. Pure power curves stay analytic, because a table is off by about 1.6 codes near black. Single-colour matrix/TRC transforms use exact f64 curves.
• No unsafe. unsafe_code is forbidden at the workspace level.
• Bounded parsing. Malformed or hostile ICC data returns an error. It never panics or allocates without limit.

Development

cargo fmt --all -- --check
cargo clippy --workspace --all-targets -- -D warnings
cargo test --workspace
cargo check --workspace --exclude tpt-colour-cli --target thumbv7em-none-eabihf   # no_std check (the CLI is std)
cargo deny check
cargo test --workspace --features tpt-colour/simd   # needs Rust 1.95
RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps

Examples live in each crate's examples/ folder. List the facade's with cargo run -p tpt-colour --example.

Release notes are in CHANGELOG.md. Contribution rules are in CONTRIBUTING.md, and vulnerability reports are in SECURITY.md.

The design is in spec.txt and the work plan in TODO.md.

Licence

Licensed under either of MIT or Apache-2.0, at your option.