feat(imaging): default to pure-Rust codecs

README.md

@@ -49,20 +49,22 @@ python3 tools/check_test_parity.py
 python3 tools/audit_red_suite.py
 ```
 
-### Optional codec features
+### Image codec features
 
 The default build needs no system image-codec library. It includes the
-project-owned TGA and DDS implementations; the default `dds-bc67` feature uses
-the pure-Rust `bcdec_rs` dependency for BC6H and BC7. Build without BC6H/BC7
-support with `cargo build -p libremetaverse --no-default-features`.
+project-owned TGA and DDS implementations, pure-Rust J2K/JP2 through
+`rust-j2k`, and pure-Rust common-raster decoding through the default
+`libremetaverse-imaging-skia` `rust-skia` feature. The default `dds-bc67`
+feature uses the pure-Rust `bcdec_rs` dependency for BC6H and BC7. Use
+`--no-default-features` only for a deliberately minimal codec-free build.
 
-The currently available opt-in codec backends are:
+The available default and optional codec backends are:
 
 | Capability | Feature | Build command | External prerequisite |
 | --- | --- | --- | --- |
-| Raw J2K and JP2 decoding/encoding through OpenJPEG | `libremetaverse/jpeg2000` | `cargo build -p libremetaverse --features jpeg2000` | OpenJPEG 2.5.4 or newer |
-| Raw J2K and JP2 decoding/encoding in pure Rust | `libremetaverse/rust-j2k` | `cargo build -p libremetaverse --no-default-features --features rust-j2k` | none |
-| BMP, GIF, ICO, JPEG, PNG, WBMP, and WebP decoding in pure Rust | `libremetaverse-imaging-skia/rust-skia` | `cargo build -p libremetaverse-imaging-skia --features rust-skia` | None |
+| Raw J2K and JP2 decoding/encoding in pure Rust (default) | `libremetaverse/rust-j2k` | `cargo build -p libremetaverse` | none |
+| BMP, GIF, ICO, JPEG, PNG, WBMP, and WebP decoding in pure Rust (default) | `libremetaverse-imaging-skia/rust-skia` | `cargo build -p libremetaverse-imaging-skia` | none |
+| Raw J2K and JP2 decoding/encoding through OpenJPEG (optional) | `libremetaverse/jpeg2000` | `cargo build -p libremetaverse --features jpeg2000` | OpenJPEG 2.5.4 or newer |
 | BMP, GIF, ICO, JPEG, PNG, WBMP, and WebP decoding through native Skia | `libremetaverse-imaging-skia/skia` | `cargo build -p libremetaverse-imaging-skia --features skia` | A matching rust-skia binary cache, or the documented native source-build tools |
 | PCM to Ogg Vorbis encoding | `libremetaverse/vorbis` | `cargo build -p libremetaverse --features vorbis` | `vorbis_rs` 0.5.6 and its native encoder build prerequisites |
 
@@ -70,9 +72,9 @@ Run their focused test suites with:
 
 ```sh
 cargo test -p libremetaverse-imaging --features jpeg2000
-cargo test -p libremetaverse-imaging --no-default-features --features rust-j2k
+cargo test -p libremetaverse-imaging
 cargo test -p libremetaverse-imaging-skia --features skia
-cargo test -p libremetaverse-imaging-skia --features rust-skia
+cargo test -p libremetaverse-imaging-skia
 cargo test -p libremetaverse --no-default-features --features vorbis
 ```
 
@@ -95,10 +97,11 @@ Deterministic task, socket, file, subscription, cancellation, and allocation
 baselines are documented in the
 [concurrency hardening guide](docs/concurrency-hardening.md).
 
-The independent `rust-j2k` backend is off by default and never enables the
-native OpenJPEG adapter. Its explicit `RustJ2kCodec` preserves the existing
-`J2kCodec` meaning when both features are enabled. Use the combined feature set
-to run backend-interoperability tests without changing application selection.
+The default `rust-j2k` backend never enables the native OpenJPEG adapter. Its
+explicit `RustJ2kCodec` preserves the existing `J2kCodec` meaning when both
+features are enabled. Likewise, default `RustSkiaTextureCodec` selection does
+not rename or enable native `SkiaTextureCodec`. The native features remain
+available for backend-interoperability testing or explicit application use.
 
 `tests/upstream-tests.json` is the machine-readable NUnit parity catalog.
 Translated tests live in hand-written Rust files with the `parity-case` marker
@@ -208,8 +211,14 @@ Legacy and DX10 BC1 through BC5 decoding is built in. The default `dds-bc67`
 feature adds BC6H/BC7 decoding through the safe, pure-Rust `bcdec_rs` crate;
 disabling default features removes that optional dependency and makes those
 two formats return a typed unsupported-format error.
-JPEG 2000 is available through the opt-in `jpeg2000` feature. It provides raw
-J2K and JP2 lossless/lossy encoding and decoding, preserves one through five
+The default `rust-j2k` feature provides raw J2K and JP2 lossless/lossy encoding
+and decoding through `RustJ2kCodec`, backed by the exact pure-Rust `j2k` 0.8.1
+release. It supports native component precision/signedness/order,
+reduced-resolution and progressive quality-layer decoding, and strict or
+explicitly permissive truncation handling. It has no C/C++ codec, CMake,
+pkg-config, vcpkg, CLR, or platform-specific API.
+The optional `jpeg2000` feature provides the native OpenJPEG alternative. It
+provides raw J2K and JP2 lossless/lossy encoding and decoding, preserves one through five
 component order, precision, signedness, and alpha metadata until explicit byte
 conversion, and bounds encoded input, output, dimensions, and decoded samples.
 The compatibility encoder reproduces CoreJ2K's four-plane RGB/alpha view,
@@ -217,20 +226,15 @@ including its alpha-only and opaque-alpha substitutions. See
 [`crates/libremetaverse-openjpeg/README.md`](crates/libremetaverse-openjpeg/README.md)
 for OpenJPEG prerequisites, licensing, and deployment details. Default builds
 do not discover or link OpenJPEG.
-The independent opt-in `rust-j2k` feature provides the same bounded public
-options through `RustJ2kCodec`, backed by the exact pure-Rust `j2k` 0.8.1
-release. It supports J2K and JP2, reversible and irreversible encoding,
-native component precision/signedness/order, reduced-resolution and progressive
-quality-layer decoding, and strict or explicitly permissive truncation handling.
-It has no C/C++ codec, CMake, pkg-config, vcpkg, CLR, or platform-specific API.
-The optional Skia adapter decodes BMP, GIF, ICO, JPEG, PNG, WBMP, and WebP into
-the same checked planar representation. Its `skia` feature uses pinned
+The default pure-Rust raster adapter decodes BMP, GIF, ICO, JPEG, PNG, WBMP,
+and WebP into the same checked planar representation through
+`RustSkiaTextureCodec`. Its optional native `skia` feature uses pinned
 rust-skia binary-cache configurations on macOS, Linux, and Windows, normalizes
 premultiplied color at the imaging boundary, and keeps encoded input, decoded
 dimensions, strides, and allocations bounded. See
 [`crates/libremetaverse-imaging-skia/README.md`](crates/libremetaverse-imaging-skia/README.md)
 for native prerequisites, cache/source-build controls, licenses, and packaging
-details. Default workspace builds do not compile or link Skia.
+details. Default workspace builds compile neither OpenJPEG nor native Skia.
 Primitive profile and path meshing is implemented in native Rust from the
 pinned `PrimMesher.cs` reference. It covers checked linear, flexible, and
 circular extrusion; profile cuts and hollows; twist, taper, shear, skew,