🦸‍♂️ webp-hero

browser polyfill for the webp image format

• 📦 npm install webp-hero
• 🎉 webp images come alive, even in safari and ie11! (firefox and edge now support webp)
• ⚙️ webp-hero actually runs google's libwebp decoder in the browser (converts webp images to png on-the-fly)
• 🕹️ live demo
  • webp-hero/ — webp-hero polyfill operating normally (does nothing if your browser supports webp)
  • webp-hero/?force — webp conversion to png is forced (even if your browser supports webp)
  • webp-hero/?force&useCanvasElements — wholly replace webp image elements with canvas elements (added for icecat compatibility)
• ♻️ freshness
  • libwebp def64e9 — 2020-08-17
  • emscripten 2.0.1 — 2020-08-21
• 💯 browser support tested 2020-08-26
  • evergreen browsers (chrome, firefox, edge, desktop safari)
  • windows 7 ie11
  • iphone 7 mobile safari
  • galaxy s5 samsung internet
  • icecat 60.7 (requires option {useCanvasElements: true})
• ⚖️ 98 KB
• ⚠️ known issues and deficiencies
  • doesn't yet support css background images (pull requests welcome!)
  • doesn't yet support <picture> elements
  • doesn't yet support web workers (decodes images one-at-a-time, blocking, single-threaded)
  • currently only detects webp images with filename ending in .webp extension
  • no wasm (because older browsers)

webp-hero installation and usage

• option A — html install, use webp-hero's bundle with the polyfills
  you just inject the html onto your page. this technique works nicely for older browsers like ie11

  1. load generic polyfills and the webp-hero global bundle via script tags

     <script src="https://unpkg.com/[email protected]/dist-cjs/polyfills.js"></script>
     <script src="https://unpkg.com/[email protected]/dist-cjs/webp-hero.bundle.js"></script>

  2. run the webp-hero polyfill function on the document

     <script>
     	var webpMachine = new webpHero.WebpMachine()
     	webpMachine.polyfillDocument()
     </script>

• option B — commonjs install, use webp-hero's cjs modules in your application
  you'll be familiar with this if you're bundling a commonjs with browserify or webpack

  1. install the webp-hero npm package

     npm install webp-hero

  2. import and run the webp-hero polyfill function

     import {WebpMachine} from "webp-hero"
     const webpMachine = new WebpMachine()
     webpMachine.polyfillDocument()

  3. if you want to support old browsers like ie11,
     you might want to include your own polyfills or import webp-hero/dist-cjs/polyfills.js

• option C — es-module install, like in the future
  es modules are available. but why would anybody use these for webp-hero? i guess it could be useful for.. mobile safari? anyways, this won't work in older browsers, which might defeat the purpose of using webp-hero in the first place? well.. it's here for you if you need it!

  1. use webp-hero on your page in one script tag

     <script type="module">
     	import {WebpMachine} from "https://unpkg.com/[email protected]/dist/webp-machine.js"
     	const webpMachine = new WebpMachine()
     	webpMachine.polyfillDocument()
     </script>

• option D — angular users should look at ngx-webp-polyfill

webp-hero advanced usage

webp-machine

• webp-machine.ts has logic for polyfilling, caching, and enforcing sequential webp decoding
  • new WebpMachine({...options}) — all options have defaults, but you can override them
    • {webp} google module which contains the actual decoder
    • {webpSupport} function which detects whether the browser supports webp
    • {detectWebpImage} detect whether or not the provided <img> element is in webp format
    • {useCanvasElements: true} boolean which when true causes webp-hero to polyfill webp images by wholly replacing them with canvas elements (instead of using png data urls). this helps compatibility with icecat (default: false)
  • the webpMachine you create has the following methods
    • webpMachine.polyfillDocument() — run over the entire html document, sniffing out webp <img> elements to convert (only if the browser doesn't support webp)
    • webpMachine.polyfillImage(imageElement) — converts the given webp image (only if the browser doesn't support webp)
    • webpMachine.decode(webpData) — decode webp Uint8Array data, return a png data-url
    • webpMachine.clearCache() — manually wipe the cache to save memory
• other modules like convert-binary-data.ts and etc may be unstable, you might not want to rely on those

manual-style with the google libwebp decoder

• we compile from google's libwebp emscripten build in a docker container
• this build contains minimal functionality for rendering webp data to a canvas:
  • google's emscripten output: webp-hero/libwebp/google/webp.js
• we do little hacks to wrap this build into two modules:
  • common-js: webp-hero/libwebp/webp.cjs.js
  • es-module: webp-hero/libwebp/webp.js
• we have a typescript declaration for it too: webp.d.ts

webp-hero dev and contributing

• prerequisites

  • git and node
  • docker (only if you want to rebuild google's libwebp)

• webp-hero development

  • npm install — install dependencies and run build
    • runs a typescript build, uses browserify to make the bundle
    • generates webp-hero/dist/ and webp-hero/dist-cjs/
    • generates the polyfills (cjs-only)
    • does not rebuild google's libwebp
  • npm start — start http server
    • visit http://localhost:5000/ to see the webp-hero demo
    • visit http://localhost:5000/libwebp/dist/google/ to see google's demo

• rebuild google's libwebp

  • libwebp build artifacts in libwebp/dist are checked into git, because it takes so damn long to build
  • libwebp/build — run dockerized libwebp build, regenerates libwebp/dist
  • libwebp/debug — handy for debugging the dockerized build