j2k 0.8.0

Pure-Rust JPEG 2000 and HTJ2K codec APIs with optional CUDA and Metal adapters
Documentation

j2k — Pure-Rust JPEG 2000 and HTJ2K Codec

JPEG 2000 Part 1 and HTJ2K Part 15 public CPU codec facade for J2K.

This crate exposes inspection, decode, encode, lossless J2K-to-HTJ2K recode, still-image container wrapping, and device-decode planning backed by the native J2K engine.

The primary adoption claim is a safe Rust public API with audited unsafe implementation boundaries and CPU as the portable correctness baseline. GPU-backed routes are optional and selected only for supported, benchmark-backed shapes; single-frame HTJ2K host-output encode stays CPU by default.

The public support boundary is raw J2K/J2C codestreams, JP2 still-image files, raw HTJ2K codestreams, and JPH still-image files. JPX / JPEG 2000 Part 2 extensions are not part of this crate's support claim unless required for standard JP2/JPH still-image correctness.

Shared encode-stage SPI types are re-exported at the crate root for CUDA, Metal, and transcode adapter interoperability. They are hidden from normal Rustdoc and are not the primary end-user encode API. Concrete device surfaces and runtime integration are provided by the j2k-cuda and j2k-metal crates.

For CPU JPEG 2000 / HTJ2K application code, use this crate directly. GPU-backed applications should also depend on the concrete adapter crate for their target backend.

Decode strictness

j2k::DecodeSettings::default() and j2k_native::DecodeSettings::default() are strict. The one-shot J2kView::parse and J2kDecoder::new paths use that default.

Compatibility callers may opt one image into DecodeSettings::lenient() with J2kView::parse_with_settings or J2kDecoder::new_with_settings. Lenient mode is deliberately narrow. It may ignore a malformed trailing top-level box after the required JP2/JPH header and codestream, ignore a malformed trailing child box after ihdr and colr, ignore malformed optional cdef or pclr metadata while preserving an earlier complete value, or infer one undeclared alpha component. Raw codestream and entropy validation, bounds and overflow checks, allocation limits, and all resource-safety checks remain strict.

Selecting lenient mode is configuration, not a warning. A successful decode reports J2kDecodeWarning::LenientMetadataRecovery only when parsing actually used one of those recoveries.

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