<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>simple Javascript WebP decoding demo, using Web-Assembly (WASM)</title>
<script type="text/javascript">
var Module = {
noInitialRun : true
};
</script>
<script type="text/javascript">
'use strict';
// main wrapper for the function decoding a WebP into a canvas object
var WebpToCanvas;
function init() {
var xhr = new XMLHttpRequest();
xhr.open('GET', 'webp_wasm.wasm', true);
xhr.responseType = 'arraybuffer';
xhr.onload = function() {
Module.wasmBinary = xhr.response;
var script = document.createElement('script');
script.src = "webp_wasm.js";
document.body.appendChild(script);
};
xhr.send(null);
}
window.onload = init;
function decode(webp_data, canvas_id) {
var result;
if (Module["asm"] != undefined) {
// wrapper for the function decoding a WebP into a canvas object
WebpToCanvas = Module.cwrap('WebpToSDL', 'number', ['array', 'number']);
// 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 decode_time = end - start;
result = 'decoding time: ' + decode_time +' ms.';
} else {
result = "WASM module not finished loading! Please retry";
}
// display timing result
var speed_result = document.getElementById('timing');
if (speed_result != null) {
speed_result.innerHTML = '<p>'+ result + '</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 demo using Web-Assembly</strong> -
</p>
<p>
WASM version of the WebP decoder, 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!"
onclick="loadfile('./test_webp_wasm.webp', 'output_canvas')">
</p>
<p id="timing">Timing: N/A</p>
<canvas id="output_canvas">Your browser does not support canvas</canvas>
</body>
</html>