lerc-rust

Pure-Rust LERC decoding for raster and elevation data. No C/C++ FFI, no build scripts, and a decoder-first API designed to be reused by container crates such as geotiff-rust.

Crates

Crate	Description
`lerc-core`	Shared types and errors for LERC blobs, decoded pixels, masks, and ndarray conversion
`lerc-reader`	Pure-Rust LERC inspection and decode paths for Lerc1 and Lerc2 blobs

Usage

use lerc_reader::{decode_ndarray, decode_mask_ndarray, get_blob_info};

let blob = std::fs::read("elevation.lerc2")?;
let info = get_blob_info(&blob)?;
println!(
    "version={:?} size={}x{} depth={} dtype={:?}",
    info.version, info.width, info.height, info.depth, info.data_type
);

let raster: ndarray::ArrayD<f32> = decode_ndarray(&blob)?;
let mask = decode_mask_ndarray(&blob)?;
println!("shape={:?} has_mask={}", raster.shape(), mask.is_some());

Concatenated band sets decode to bands-last arrays:

let rgb: ndarray::ArrayD<u8> = lerc_reader::decode_band_set_ndarray(&blob)?;
assert_eq!(rgb.shape(), &[height, width, bands]);

Supported Now

Lerc1 header parsing, mask decoding, tiled block decode, and concatenated shared-mask band sets
Lerc2 header parsing, Fletcher32 verification, mask decoding, constant/raw, tiled, bit-stuffed, and Huffman decode paths
Native typed decode and type-promoting f64 decode
Direct ndarray::ArrayD conversion for rasters, band sets, and masks
Shape helpers and shared metadata types in lerc-core

Testing

cargo fmt --all --check
cargo clippy --workspace --all-targets -- -D warnings
cargo test --workspace

Interop fixtures are vendored in the repository under testdata/interoperability. The default test suite covers:

synthetic decoder-path unit tests embedded in lerc-reader
official Esri fixtures for Lerc1, masked Lerc2, and concatenated multi-band Lerc2
an Esri JavaScript sanity fixture for depth > 1

Reference-library parity tests compare lerc-reader against Esri's official libLerc decoder when a compiled helper path is configured; otherwise they self-skip:

LERC_READER_REFERENCE_HELPER="$(./scripts/build-reference-helper.sh)" \
  cargo test -p lerc-reader --test reference_parity

For a reproducible reference environment, run the Docker harness:

./scripts/run-reference-parity.sh

Criterion comparison benches against libLerc live in lerc-reader/benches/reference_compare_bench.rs:

./scripts/run-reference-benchmarks.sh

For methodology and current benchmark notes, see the repository copy of docs/benchmark-report.md.

License