Thumbnails are now generated eagerly as lossy WebP (the primary codec) and
served to clients that advertise `Accept: image/webp`; JPEG is kept as a lazy
fallback for older clients and NextCloud, generated on first request and then
cached like WebP.
- ThumbnailFormat{Webp,Jpeg} enum threaded through encode/render/generate, the
on-disk path ({hash}.webp / {hash}.jpg), the moka cache key
(file_id, size, format), and cleanup (both formats removed).
- file_handler: parse Accept -> format, format-keyed ETag, `Vary: Accept` on
every response (incl. 304) so shared caches never serve the wrong codec;
Content-Type is byte-sniffed (infer) so it always matches the bytes.
- preview_handler (NextCloud) pins JPEG.
- webp = "0.3" (vendored libwebp via cc, no system dependency).
WEBP_QUALITY=82, chosen via a quality sweep (bench Table E1): SSIM within
~0.005 of JPEG q80 (imperceptible at thumbnail scale) for ~62% fewer bytes. On
the photo-realistic bench corpus the full set (3 sizes x 3 photos) drops 65.6%
(213->73 KB); real photos with edges/text land nearer ~25-40%. Encode is +5ms,
paid once in the eager background generator (off the request path).
The bench corpus is now photo-realistic (per-channel sums of low-frequency
sinusoids) instead of white noise, which had distorted codec byte ratios.
Methodology + numbers in benches/WEBP.md.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Replace the image crate's scalar resampler with fast_image_resize
(AVX2/SSE4.1/NEON) in a shared encode_thumbnail() helper. render_all now
converts to RGB8 once and SIMD-resizes the shared buffer per size. Lanczos3 for
downscaling, CatmullRom when upscaling (Lanczos rings on enlargement).
Also folds the duplicated path-variant generate_all_sizes_background into the
shared render path -- it had missed BOTH shrink-on-load and SIMD resizing -- so
every thumbnail path now goes through one optimised routine (no duplication).
Measured on 14 cores vs the post-1.5 state (benches/BASELINE.md):
- PNG 2.60x faster (33.6->12.9ms), GIF/WebP 1.25-1.6x: full-resolution decode
paths where the resize dominates, so SIMD helps most
- JPEG only ~7% (shrink-on-load already shrank the bitmap) but peak heap fell
another ~2.5x (17.6->7.1MB): tight RGB buffers, RGB conversion once
- quality SSIM 0.986-0.994 at identical dims (>=0.98 gate)
Thumbnails are now exactly max_dim on the long side (e.g. 400x266) vs the old
fit-within 399x266 -- a <=1px change, invisible under object-fit: cover.
Bench example gains an exact-dims quality reference + semaphore throughput table.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Shrink-on-load decoupled peak heap from source resolution (~18-25 MB per decode
regardless of MP), so the RAM ceiling that justified halving decode concurrency
is gone. max_concurrent_decodes() now defaults to all cores, with an
OXICLOUD_THUMBNAIL_DECODE_CONCURRENCY override for ops tuning.
Measured on the real service path (Semaphore + spawn_blocking), 14 cores:
- 12MP: 92.7 -> 133.7 photos/s (1.44x)
- 24MP: 49.5 -> 69.9 photos/s (1.41x)
peak heap unchanged; cpus*2 yields nothing, confirming cpus is the right ceiling
for CPU-bound work (the gap to 2x is rayon oversubscription -- Task 1.7).
Adds a semaphore-bounded throughput harness (Table D) to the bench example.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Decode JPEGs at the smallest DCT scale (1/8·1/4·1/2·1/1) whose long axis is
still ≥ the largest needed thumbnail (800px), via jpeg-decoder, instead of a
full-resolution decode through the image crate. The full-res bitmap — the
dominant time and RAM cost — is never materialised. PNG/GIF/WebP and unusual
JPEG colour spaces (CMYK / 16-bit grey) fall back to a full decode.
Extracts the shared decode + EXIF-orientation logic into decode_oriented(),
removing the duplication that existed between render_thumbnail_from_data and
render_all_thumbnails_from_data.
Measured on 14 cores (see benches/BASELINE.md):
- render_all 1.8-2.0× faster (12MP 111->61ms, 48MP 398->203ms)
- peak heap 5.5-14.8× lower, now decoupled from source MP (~18-25MB regardless)
- saturated throughput 3-3.6× (parallel efficiency 4.9×->8.5×)
- quality SSIM 0.987-0.999 (>=0.98 gate), PSNR 47-55dB
Also adds the Phase 0 benchmark harness (gated behind the `bench` feature, zero
prod impact): deterministic image corpus (src/bench_support.rs), criterion
latency bench (benches/thumbnails.rs), and a peak-RAM/throughput/SSIM harness
(examples/bench_thumbnails_mem.rs). Baseline + before/after in benches/BASELINE.md.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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