Safe Rust APIs / Optional CUDA + Metal

JPEG 2000and HTJ2K

Safe public Rust APIs for JPEG 2000 Part 1 and HTJ2K Part 15 inspection, decode, encode, recode, and coefficient-domain JPEG-to-HTJ2K transcode workflows.

CPU is the correctness baseline. CUDA and Apple Metal backends accelerate supported paths.

crates.io API docs Repository

Release statusSee the changelog and crates.io for the current published version.

01 / Public surface

What J2K provides

Memory safety

Safe public Rust APIs

Applications use a safe Rust API. Unsafe implementation code is limited to documented FFI, GPU, SIMD, allocation, and pointer or buffer boundaries.

Routing

GPU-accelerated backends

Applications keep a portable CPU path and can send supported workloads to CUDA or Apple Metal.

Licensing

MIT or Apache-2.0

The workspace is dual-licensed for use in open-source and commercial projects.

02 / Architecture

How J2K runs

J2K/JP2 and HTJ2K/JPH still images are handled by one crate. The CPU path is the reference implementation; CUDA and Metal speed up the shapes they support.

J2K pipeline: JPEG 2000, HTJ2K, and JPEG inputs flow through the j2k crate, which routes to CPU baseline, CUDA, and Metal backends. — `Auto` returns CPU output when no GPU path is available, supported, or measured faster for the shape. Explicit CUDA and Metal requests never fall back.

03 / Supported formats

Supported formats

Exact coverage is maintained in the public support matrix.

In scope

JPEG 2000 Part 1

Raw J2K/J2C codestream parse, inspect, decode, encode, ROI, progression, tile-part, packet-marker, signed, high-bit, and component-plane surfaces are tracked by the public support matrix.

In scope

HTJ2K Part 15

HT cleanup and refinement decode/encode, quality layers, rate behavior, raw HT codestreams, and JPH still-image wrapping are in scope.

Limits

Wrappers and limits

JP2 and JPH still-image metadata is supported. JPX / JPEG 2000 Part 2 extensions are not.

The full support table is in docs/public-support.md. Benchmark results are in docs/benchmark-evidence.md; comparisons with other codecs use pinned external corpora.

04 / Install

Install

Most applications should start with the public facade crate. The CLI is useful for inspection and conservative JPEG-to-HTJ2K transcode smoke tests.

Library01

$ cargo add j2k

Safe public APIs for inspection, decode, encode, recode, JP2, and JPH.

CLI smoke test02

$ cargo install j2k-cli
$ j2k inspect input.jp2
$ j2k transcode input.jpg output.j2k \
    --htj2k --lossless-53

05 / Workspace

Package map

Crate	Role	Layer
`j2k`	Public API for JPEG 2000 Part 1 / HTJ2K Part 15 inspection, decode, encode, recode, JP2, and JPH.	Public
`j2k-cuda`	NVIDIA CUDA backend for supported JPEG 2000 and HTJ2K paths.	Backend
`j2k-metal`	Apple Metal backend for supported macOS GPU paths.	Backend
`j2k-transcode`	JPEG-to-HTJ2K coefficient-domain transcode primitives and shared transcode contracts.	Core
`j2k-cli`	Command-line inspection and JPEG-to-HTJ2K transcode smoke tests.	Tool

06 / Documentation