bext-plugin-image-opt

On-the-fly image optimization with WebP/AVIF conversion and blur placeholders.

Intercepts image responses and optimizes them on the fly. Converts to WebP or AVIF based on the client's Accept header. Generates blur placeholder data URIs for above-the-fold images. Compiled to WASM for near-native performance.

Install

bext plugin add image-opt

Config

[plugins.image-opt]
quality = 80
max_width = 2048
formats = ["webp", "avif"]
blur_placeholders = true
cache_ttl = "7d"

How it works

The plugin hooks into `onResponse`. When it sees a response with an image content-type, it:

1. Checks the request's `Accept` header for WebP/AVIF support 2. Resizes if the image exceeds `max_width` 3. Re-encodes in the best supported format 4. Sets aggressive cache headers 5. Optionally generates a 32px blur placeholder and stores it in a response header (`X-Blur-Hash`)

Images that are already smaller than the optimized version are passed through untouched.

Supported formats

Input: JPEG, PNG, GIF, BMP, TIFF, WebP. Output: WebP, AVIF, or original format if neither is accepted.

Performance

The WASM sandbox adds ~2ms overhead per image on first request. Subsequent requests hit the CDN cache.