feat(imaging): add pure-Rust JPEG 2000 backend (#109)

crates/libremetaverse-imaging/Cargo.toml

@@ -10,10 +10,12 @@ description = "Texture codec abstractions for the MetaCrate LibreMetaverse rewri
 [features]
 default = []
 jpeg2000 = ["dep:libremetaverse-openjpeg"]
+rust-j2k = ["dep:j2k"]
 
 [dependencies]
 libremetaverse-types = { version = "0.0.1", path = "../libremetaverse-types" }
 libremetaverse-openjpeg = { version = "0.0.1", path = "../libremetaverse-openjpeg", optional = true }
+j2k = { version = "=0.8.1", optional = true }
 
 [dev-dependencies]
 stats_alloc = "0.1.10"

crates/libremetaverse-imaging/src/lib.rs

@@ -1,14 +1,15 @@
 //! Image and texture abstractions corresponding to `LibreMetaverse.Imaging`.
 //!
 //! The default surface provides managed images plus native `TGA`/`DDS` handling.
-//! Enable `jpeg2000` only when the audited system `OpenJPEG` adapter is available;
-//! ordinary users can consume the traits without a native image dependency.
+//! Enable `jpeg2000` for the audited system `OpenJPEG` adapter or `rust-j2k`
+//! for the independently selectable pure-Rust JPEG 2000 backend. Ordinary
+//! users can consume the traits without either codec dependency.
 
 extern crate self as libremetaverse_imaging;
 
 pub mod codec;
 
-#[cfg(feature = "jpeg2000")]
+#[cfg(any(feature = "jpeg2000", feature = "rust-j2k"))]
 mod jpeg2000;
 
 mod generated;
@@ -16,6 +17,10 @@ mod managed_image;
 
 pub use generated::*;
 #[cfg(feature = "jpeg2000")]
-pub use jpeg2000::{J2kCodec, J2kCompression, J2kDecodeOptions, J2kEncodeOptions, J2kFormat};
+pub use jpeg2000::J2kCodec;
+#[cfg(feature = "rust-j2k")]
+pub use jpeg2000::RustJ2kCodec;
+#[cfg(any(feature = "jpeg2000", feature = "rust-j2k"))]
+pub use jpeg2000::{J2kCompression, J2kDecodeOptions, J2kEncodeOptions, J2kFormat};
 pub use libremetaverse_types::Error;
 pub use managed_image::{DEFAULT_MAX_ENCODED_BYTES, DEFAULT_MAX_PIXELS};