html5 worker example (2) image transformation effect-HTML Tutorial-php.cn

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html5 worker example (2) image transformation effect

黄舟

Dec 20, 2016 pm 02:59 PM

html5

Worker’s js code img.js

onmessage = function(e) { 
postMessage(filter(e.data)) 
}; 
function filter(imgd) { 
var pix = imgd.pixels.data; 
var xcord = imgd.x / 1000; 
var ycord = imgd.y / 1000; 
for ( var i = 0, n = pix.length; i < n; i += 4) { 
var grayscale = pix[i] * xcord + pix[i + 1] * .59 + pix[i + 2] * .11; 
pix[i] = grayscale; // red 
pix[i + 1] = grayscale; // green 
pix[i + 2] = grayscale; // blue 
} 
imgd[&#39;pixels&#39;].data = pix; 
return imgd; 
}

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html code

<!DOCTYPE html> 
<html> 
<head> 
<title>test2.html</title> 
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 
<meta http-equiv="description" content="this is my page"> 
<meta http-equiv="content-type" content="text/html; charset=UTF-8"> 
<!--<link rel="stylesheet" type="text/css" href="./styles.css">--> 
<script type="text/javascript" src="../js/jquery-1.8.0.min.js"></script> 
</head> 
<body> 
<canvas id="myCanvas" width="640" height="480"></canvas> 
<img src="../image/psu[4].jpg" class="onHover"> //注意，自己在这里插入一张图片，否则没用效果 
<script type="text/javascript"> 
function process(img,x,y){ 
var canvas = document.getElementById("myCanvas"); 
var context = canvas.getContext(&#39;2d&#39;); 
context.drawImage(img, 0, 0); 
var pixels = context.getImageData(0,0,img.width,img.height); 
var worker = new Worker("img.js"); 
var obj = { 
pixels: pixels, 
x:x, 
y:y 
} 
worker.postMessage(obj); 
worker.onmessage = function(e) { 
if (typeof e.data === "string") { 
console.log("Worker: " + e.data); 
return; 
} 
var new_pixels = e.data.pixels; // Pixels from worker 
context.putImageData(new_pixels, 0, 0); 
img.src = canvas.toDataURL(); // And then to the img 
} 
} 
</script> 
<script type="text/javascript"> 
$(function(){ 
$(".onHover").on("mouseover", function(){ 
var x =this.width; 
var y = this.height; 
console.log("X: " + x + " Y: " + y); 
process(this, x, y); 
}); 
}) 
</script> 
</body> 
</html>

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When executing the above example, you need to introduce the jquery package yourself and put the image you want to transform on the img tag on the html page. Then deploy it to the server, open the page, and when the mouse moves over the picture, the transformation will occur. The function that performs the transformation function here is responsible for the worker, which does not affect the efficiency of the page itself, similar to multi-threading in the Java language.

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