CPU baseline
Portable CPU paths remain available for general JPEG 2000 / HTJ2K application code and for unsupported device shapes.
GPU backends
Vendor-Independent GPU JPEG2000 Rust
J2K treats GPU acceleration as an optional backend layer: CPU decode and encode remain the correctness baseline, while CUDA and Apple Metal adapters cover supported JPEG 2000 / HTJ2K paths.
Release status: j2k 0.8.0 is published on crates.io; see the release policy for support details.
CUDA
j2k-cuda, j2k-jpeg-cuda, and j2k-transcode-cuda integrate J2K-owned kernels, CUDA device surfaces, and strict route policy for supported shapes.
Metal
j2k-metal, j2k-jpeg-metal, and j2k-transcode-metal integrate Apple Metal-backed paths on macOS under the same support boundary.
Strict backend behavior
BackendRequest::Auto may choose CPU for unsupported or unbenchmarked shapes. Explicit CUDA or Metal requests are strict and report unsupported paths clearly.
The codec support boundary is the same as the CPU baseline: JPEG 2000 Part 1 codestreams, JP2 still-image files, HTJ2K Part 15 codestreams, and JPH still-image files. GPU adapters accelerate selected shapes inside that boundary; they are not a separate promise of full-device coverage.
Use docs/public-support.md for codec support. Current public benchmark evidence is in docs/benchmark-evidence.md; adoption-facing speed claims require a completed external bundle with publication_eligible=true.