j2k-metal

Apple Metal GPU adapter for Rust JPEG 2000 / HTJ2K decode and encode-stage paths on macOS.

The crate provides resident Metal decode and encode-stage integration for supported workloads. It uses j2k-metal-support for runtime setup while keeping codec-specific kernels local.

Encode support is stage-oriented unless a documented resident path accepts the shape. Auto host-output encode may dispatch benchmark-gated coefficient-prep stages for 512 x 512 and larger stage inputs, and the resident HTJ2K RGB8 lossless shortcut is gated to 1,024 x 1,024 and larger tiles. Explicit Metal requests are strict: supported shapes dispatch, and unsupported direct Metal requests return UnsupportedMetalRequest instead of silently changing backend.