oximg

High-performance image compression in Rust: a library, a CLI, and a self-hostable HTTP server (PoC). JPEG, PNG, WebP — and AVIF with the avif feature — in and out; sources are format-sniffed by magic bytes and re-encoded in their own format. On imgproxy's official benchmark harness, run on the same AWS instance types as their published results, oximg leads every format cell on both x86-64 and Graviton while resizing in linear light at measurably higher output quality (see Benchmarks).

Features

• HTTP resize service: GET /resize/{w}/{h}/{file} fits the source within w x h (never enlarges) and re-encodes it in its own format. Sources come from a local directory or any HTTP(S) origin (OXIMG_SOURCE_BASE_URL), where decoding overlaps the download. Optional imgproxy-style HMAC URL signing.
• Quality-first processing: resizing happens in linear light on 16-bit samples with Lanczos3, JPEG sources are decoded supersampled (DCT shrink-on-load kept ≥ 1.7x the target), and alpha is premultiplied across the resample — the properties behind the SSIMULACRA2 scores in Benchmarks.
• Performance as architecture, not flags: per-arch row-streaming SIMD resize kernels (AVX2 on x86-64, NEON on aarch64, both verified against an f64 reference), JPEG decode fused with resize+encode on a second thread under low load, request coalescing for concurrent identical URLs, and CPU concurrency pinned to the core count. Peak memory stays at a fraction of imgproxy's under identical load (BENCH.md).
• Tunable profiles: the default maximizes quality per byte (progressive jpegli); one env flip (OXIMG_JPEG_PROGRESSIVE=0) trades ~10% output size for the lowest latency at unchanged pixels. PRESET=fast|small selects mozjpeg profiles instead.
• Self-contained deploys: multi-arch Docker images (linux/amd64 + linux/arm64) on Docker Hub (oximg/oximg) and GHCR (ghcr.io/oximg/oximg); a single static-leaning binary otherwise.

Supported formats

Sources are identified by magic bytes (extensions are never trusted). By default the output format is the source's own; any decode column combines with any encode column:

Cross-format output: append an imgproxy-style @{fmt} token to the filename — /resize/300/200/photo.jpg@webp (jpg/jpeg, png, webp, avif; jxl is reserved). Only exact tokens count, so photo@2x.jpg is still a filename. Precedence: explicit @{fmt} > Accept negotiation > source format. Negotiation is opt-in: set OXIMG_AUTO_FORMAT to a preference list (e.g. avif,webp) and bare-URL responses follow the request's Accept header; every response then carries Vary: Accept (make sure your CDN honors it or normalizes Accept into the cache key — explicit @{fmt} URLs avoid the issue entirely, which is what signed deployments should prefer since headers are outside the signature). Alpha sources encoded to JPEG are flattened in linear light onto OXIMG_FLATTEN_BG (hex RRGGBB, default white). Encode settings are keyed by the output format, using the same knobs as same-format requests.

Orientation: every source format auto-rotates — JPEG EXIF, PNG eXIf, WebP EXIF chunks, and AVIF irot/imir transforms. The target box applies to the displayed frame and the pixels come out upright in every output format (the metadata itself is not forwarded, so nothing double-rotates). OXIMG_AUTO_ROTATE=0 restores the raw stored orientation.

ICC profiles: a source's color profile (JPEG APP2 chain, PNG iCCP, WebP ICCP, AVIF colr) passes through byte-for-byte into any output format, across format conversion included. Pixels are never color-converted. This matters for wide-gamut sources: the common proxy default is to normalize pixels to sRGB and strip the profile, which permanently clips every color outside the sRGB gamut — a Display P3 phone photo loses exactly the saturated reds and greens that made it worth shooting in P3. oximg keeps the pixels and the profile as they were, so wide-gamut images render on a wide-gamut display the way the original did (and identically everywhere else). OXIMG_ICC=0 opts into stripping instead.

Pipeline

source bytes (local file or HTTP origin)
  → format sniff → decode
      JPEG: mozjpeg streaming decode, DCT shrink-on-load (kept ≥ 1.7x target size)
      PNG:  png crate (palette/gray/16-bit normalized to RGB(A)8)
      WebP: libwebp
      AVIF: dav1d (8/10/12-bit, all subsamplings, alpha, bilinear chroma upsampling)
  → linear-light resize: sRGB u8 → linear u16 → Lanczos3 → sRGB u8
      (alpha is premultiplied before resampling, unpremultiplied after;
       JPEG rows stream through in-tree ring-scheduled f32 row kernels —
       AVX2 on x86-64, NEON on aarch64, both verified against an f64
       reference — optionally fused with the decode on a second thread;
       other formats resize full-frame: pic-scale on x86-64, the same
       in-tree kernel on aarch64)
  → encode in the source format
      JPEG: jpegli, progressive (PRESET=fast / PRESET=small select mozjpeg profiles)
      PNG:  png crate | WebP: libwebp | AVIF: SVT-AV1 (10-bit 4:2:0, tune=ssim)

Concurrent identical requests are coalesced and share one result. CPU concurrency is pinned to the core count with a semaphore; the HTTP layer (axum/tokio) only does queueing and IO.

Benchmarks

imgproxy's official harness (DIV2K corpus over nginx, fit into 512x512, k6, all defaults) on the AWS instance types behind imgproxy's published numbers — req/s, higher is better, p95 in parentheses:

Cross-format cells (our harness extension; JPEG sources, oximg vs imgproxy):

At the same time, output quality is higher, not traded away: end-to-end JPEG at the same q80 scores +6 to +18 SSIMULACRA2 over imgproxy (77.5 vs 71.2 on the Kodak corpus, the gap widening with source size — and imgproxy at q90 with twice the bytes still scores lower), pure resize quality (lossless PNG path) scores 97.6 vs 81.9, and the AVIF default produces smaller files than imgproxy's default at +6.7 SSIMULACRA2.

• BENCH.md — full methodology and tables: official harness (local and AWS), sustained-load and memory measurements, presets.
• bench/quality/QUALITY.md — output quality (SSIMULACRA2) at matched settings vs imgproxy and sharp.

Usage

Docker (recommended — multi-arch linux/amd64 + linux/arm64, AVIF included; both registries rebuild on every main push):

docker run -p 8081:8081 -v $PWD/images:/images:ro ghcr.io/oximg/oximg:latest
# or: docker.io/oximg/oximg:latest
curl "localhost:8081/resize/500/500/photo.jpg" -o out.jpg

Homebrew (builds v0.4.2 from source; JPEG/PNG/WebP, no AVIF):

brew install oximg/tap/oximg

Cargo (crates.io, v0.4.2; add --features avif if SVT-AV1 >= 4.1 and dav1d are installed and visible to pkg-config):

cargo install oximg

Note the release channels lag main: crates.io and the brew formula ship the last tagged release, while the Docker images rebuild on every main push. The npm package @oximg/oximg is a name reservation that points here.

From source:

cargo build --release            # JPEG, PNG, WebP
cargo build --release --features avif   # + AVIF (needs SVT-AV1 >= 4.1, dav1d)
IMAGES_DIR=./images PORT=8081 QUALITY=80 ./target/release/oximg

The Docker build needs no system dependencies — it compiles a pinned post-4.1 SVT-AV1 revision that carries the aarch64 kernels for the still-image path:

docker build -t oximg .

URL signing (optional): set OXIMG_KEY and OXIMG_SALT (hex) to require imgproxy-style signed URLs — /{base64url(HMAC-SHA256(key, salt || path))}/resize/{w}/{h}/{file}.

Environment variables: PORT (8081), IMAGES_DIR (./images), OXIMG_SOURCE_BASE_URL (fetch sources from <base>/<file> over HTTP instead of the local filesystem; streaming decode overlaps the download), OXIMG_MAX_SOURCE_BYTES (64MiB), QUALITY (JPEG quality, 80), OXIMG_WEBP_QUALITY (75), OXIMG_AVIF_QUALITY (55), OXIMG_AVIF_ALPHA_QUALITY (same as color), OXIMG_AVIF_SPEED (SVT preset, 8; setting 9 trades ~-0.6 SSIMULACRA2 at unchanged bytes for ~28% less encode CPU — measured +19% JPEG→AVIF req/s on a real c7i.large, ahead of imgproxy by +16%; see BENCH.md and bench/quality/QUALITY.md), PRESET (jpegli default; fast = mozjpeg baseline profile, small = mozjpeg trellis+progressive), OXIMG_AUTO_FORMAT (unset; comma-separated Accept-negotiation preference list, e.g. avif,webp), OXIMG_FLATTEN_BG (ffffff; background for alpha → JPEG flattening), OXIMG_AUTO_ROTATE (1; 0 serves the stored orientation), OXIMG_ICC (1; 0 strips source ICC profiles from outputs; the shared JPEG header scan is skipped only when both knobs are off), OXIMG_RESIZE=srgb (resize in sRGB space instead of linear light), OXIMG_RESIZE_BACKEND=fir (use the portable fast_image_resize convolution instead of the platform kernel), OXIMG_AVIF_DECODE_THREADS (dav1d workers; defaults to 2 on x86-64 where SMT absorbs the second thread and 1 on SMT-less aarch64), OXIMG_DCT_MARGIN (1.7), OXIMG_PAR (resize threads, 1), OXIMG_PNG_EFFORT (fast; fastest/balanced/high trade PNG size against encode time), OXIMG_WEBP_EFFORT (libwebp method, 2), OXIMG_WEBP_DECODE_THREADS (1; 0 disables libwebp's two-thread decode pipelining), OXIMG_TIMING (set to print per-stage timing lines to stderr), OXIMG_LOG (error: one stderr line per failed request, always on; request also logs successes, with a request id and wall time), OXIMG_OVERLAP (JPEG requests fuse decode with resize+encode on a second thread, cutting single-request latency ~20%; the default auto fuses while 2 x active requests <= visible CPUs and falls back to one core per request under contention. Serial and fused stream through the same SIMD kernel, so a URL's bytes are identical either way; 1 forces fusing, 0 disables it), OXIMG_JPEG_PROGRESSIVE (0 selects baseline jpegli: a few percent larger JPEG output — still at or below libjpeg-turbo size for the same input, at higher quality — in exchange for moving jpegli's entropy pass off the latency tail: combined with OXIMG_OVERLAP this is the speed profile, ~-13% single-request latency and ~+9% saturated throughput over the default).

Not yet implemented (out of PoC scope)

• JXL output (the @jxl token is reserved and returns a clear error)
• Animated output (animated AVIF and WebP sources render their first frame, like other image proxies)
• Private S3 sources (public/presigned HTTP origins work), caching
• Production-grade load testing

Status

Experimental PoC — APIs and the HTTP interface will change without notice. The @oximg npm package is a name reservation.

License

Apache-2.0.

The compiled binary statically links third-party code (jpegli/libjxl — BSD-3-Clause, Highway — Apache-2.0, mozjpeg/libjpeg-turbo — IJG). Their license texts and required notices are bundled in THIRD-PARTY-LICENSES.md, generated with cargo about. Dependency licensing is gated in CI by cargo deny (deny.toml).