This is a JPEG XL decoder in JavaScript using WebAssembly implementation from the Squoosh app running in Web Worker.
Just insert your JPEG XL images to your HTML document as usual: <img src="image.jxl" alt="..." width="..." height="..."> and append the minified JXL.js script to the <head> of your web page:
<script src="jxl.min.js"></script>
That's it!
You can enable/disable cache and choose target image type (JPEG/PNG/WebP) by editing config at the beginning of jxl.js file.
JXL.js uses Mutation Observer to watch for <img> tags being added to the DOM as well as CSS background images and it decodes them as they appear using WebAssembly decoder in Web Worker. Then the JPEG XL image data is transcoded into JPEG/PNG/WebP image and cached using Cache API for faster subsequent page views. The transcoding is performed using Offscreen Canvas in Web Worker for jank-free performance, if available.
There is an experimental multithread version of JXL.js using Web Workers and WebAssembly SIMD operations, if available, based on the libjxl wasm demo. Requires HTTPS as well as Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy response headers (or the provided Service Worker script as a fallback).
© 2022 Jerzy Głowacki and Squoosh Developers under Apache 2.0 License.