Image Load Lab — measured responsive image candidates

Run date: 2026-08-12
Source: ill-format-benchmark-source.png, 1280 × 800 RGB, 1734570 bytes
Source SHA-256: 8ee761ff7a23c8ecccec1c2acf8db61dc975fca184e769169e01af4f35394da6
Environment: Node.js v24.14.0; Sharp 0.34.5; libvips 8.17.3; WebP 1.6.0

Method
1. Decode the same source PNG for every candidate.
2. Resize to 480, 768, 1024, 1280 pixels wide with libvips lanczos3 and without enlargement.
3. Encode every candidate as WebP quality 80, effort 6, smart subsampling enabled.
4. Record actual output dimensions, bytes and SHA-256 hashes.
5. Open the included currentSrc demo at the target viewport and DPR. Treat slot × DPR as an expectation and browser currentSrc as the observation.

Limitations
- The candidate byte sizes belong to this fixture and encoder build.
- Browser selection may vary with DPR, zoom, cache, data-saving behavior and implementation.
- The source is 1280 pixels wide, so the widest candidate deliberately caps demand instead of upscaling to 1520 or 1600 pixels.
