third_party/libwebp/webp_js/index.html

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>simple Javascript WebP decoding demo</title>
  <script type="text/javascript">
    var Module = {
      noInitialRun : true
    };
  </script>
  <script type="text/javascript" src="./webp.js"></script>
  <script type="text/javascript">

'use strict';

// main wrapper for the function decoding a WebP into a canvas object
var WebpToCanvas;

function init() {
  WebpToCanvas = Module.cwrap('WebpToSDL', 'number', ['array', 'number']);
}
window.onload = init;

function decode(webp_data, canvas_id) {
  // get the canvas to decode into
  var canvas = document.getElementById(canvas_id);
  if (canvas == null) return;
  // clear previous picture (if any)
  Module.canvas = canvas;
  canvas.getContext('2d').clearRect(0, 0, canvas.width, canvas.height);
  // decode and measure timing
  var start = new Date();
  var ret = WebpToCanvas(webp_data, webp_data.length);
  var end = new Date();
  var speed_result = document.getElementById('timing');
  // display timing result
  if (speed_result != null) {
    var decode_time = end - start;
    speed_result.innerHTML = '<p>decoding time: ' + decode_time +' ms.</p>';
  }
}

function loadfile(filename, canvas_id) {
  var xhr = new XMLHttpRequest();
  xhr.open('GET', filename);
  xhr.responseType = 'arraybuffer';
  xhr.onreadystatechange = function() {
    if (xhr.readyState == 4 && xhr.status == 200) {
      var webp_data = new Uint8Array(xhr.response);
      decode(webp_data, canvas_id);
    }
  };
  xhr.send();
}
  </script>
</head>

<body>
  <p>
    <strong>WebP in JavaScript demo</strong> -
  </p>
  <p>
    WebP decoder in JavaScript, using libwebp compiled with
    <a href="https://github.com/kripken/emscripten/wiki">Emscripten</a>.
  </p>
  <p id="image_buttons">
    <input type="button" value="test image!" name="./test_webp_js.webp"
           onclick="loadfile(this.name, 'output_canvas')">
  </p>
  <p id="timing">Timing: N/A</p>
  <canvas id="output_canvas">Your browser does not support canvas</canvas>

</body>
</html>