Changelog

Copy Markdown View Source

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

Unreleased

0.1.0 - 2026-06-26

Added

  • Butteraugli.compare/5 and compare!/5 — compute the butteraugli perceptual difference between two packed-binary images, returning a Butteraugli.Result with score (max-norm distance), pnorm_3 (libjxl 3-norm aggregation), and an optional diffmap.
  • Butteraugli.Reference — new/4, new!/4, compare/3, compare!/3 for reusing one prepared reference across many candidates (~2× faster per compare in a quality-search loop). compare/3 takes prefer: :speed | :memory (default :speed); :memory runs a strip-bounded walker with bounded peak memory and per-strip cancellation, trading away the speedup.
  • Input formats selectable via the :format option: :rgb888 (default, u8 sRGB) and :linear_rgb (f32 linear RGB).
  • Tuning parameters :intensity_target (display brightness in nits, crate default 80.0) and :hf_asymmetry (added-vs-removed high-frequency weighting, crate default 1.0). On Butteraugli.Reference these are baked in at new/4 time.
  • Optional difference map via :compute_diffmap (default false). Diffmaps are cropped back to the input size; images smaller than 8×8 are padded up to butteraugli's 8×8 floor and scored.
  • Cooperative cancellation: Butteraugli.CancelRef.new/0 and Butteraugli.cancel/1. The metric runs on a dirty scheduler and polls the cancel ref at strip boundaries, freeing the CPU promptly. A cancel ref is single-use and can cover a whole batch.
  • Wall-clock timeouts via the :timeout option, returning {:error, :timeout}.
  • Optional Vix integration (Butteraugli.Vix.compare/2, Butteraugli.Vix.reference/2), available when :vix is a dependency; images are coerced to 8-bit sRGB.
  • Precompiled NIFs via rustler_precompiled for aarch64/x86_64 macOS, gnu/musl Linux, and x86_64 Windows, across NIF versions 2.15–2.17, so the Rust toolchain is not required on covered targets.

Notes

  • butteraugli is pinned to a git revision because the cooperative-cancellation API (*_with_stop) has not yet landed in a crates.io release. This will move to a versioned dependency once available.
  • The underlying crate is a port of Google's butteraugli implementation from libjxl.