html5 worker 实例(二) 图片变换效果

【 tulaoshi.com - Web开发 】

worker的js代码img.js

代码如下：

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['pixels'].data = pix;
return imgd;
}

html代码

代码如下：

!DOCTYPE html
html
head
titletest2.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('2d');
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

是执行上面的例子的时候 ，要自己引入jquery包，并且在html页面上的img标签上放入自己要变换的图片。然后部署到服务器，打开页面，当鼠标移动到图片的 上面的时候就会发生变换，在这里执行变换功能的函数有worker负责，随意不影响页面本身的效率，类似于java语言中的多线程。