javascript - js drawImage如何產生圖片撕裂閃爍，以下程式碼的邏輯是如何實現的
可直接開啟連結看效果：http://evilzone.org/。以下是它的程式碼
<!DOCTYPE html>
<!-- saved from url=(0020)http://evilzone.org/ -->
<html><!-- Hello :) --><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Evilzone - Hacking and Security Network</title>
<style>
body {
height: 100%;
width: 100%;
margin: 0;
padding: 0;
background-color: #191919;
font-family: Arial, Helvetica, sans-serif;
}
.box {
color: #c8c8c8;
padding: 20px;
margin: 20px;
border: solid #404040 1px;
outline: solid #101010 1px;
background-color: #252525;
width: 610px;
margin-left: auto;
margin-right: auto;
margin-top: 50px;
}
.leCanvas {
border: solid #404040 1px;
outline: solid #101010 1px;
background-color: #202020;
padding: 10px;
}
</style>
</head>
<body>
<p class="box">
<canvas id="canvas" class="leCanvas" width="590" height="128"></canvas>
</p>
<script>
var canvas = document.getElementById('canvas')
, context = canvas.getContext('2d')
, img = new Image()
, w
, h
, offset
, glitchInterval;
img.src = 'logo.png';
img.onload = function() {
init();
window.onresize = init;
};
var init = function() {
clearInterval(glitchInterval);//清除定时器
canvas.width = w = img.width;//将图片的宽度赋值给w，并将画布的宽度设为图片的宽度
offset = w * .1;//设置偏移量为w*0.1
canvas.height = h = img.height;//将画布的高度设为图片的高度
glitchInterval = setInterval(function() {
clear();//每一帧清除前一帧
context.drawImage(img, 0, 0, img.width, img.height);//将图片全部剪切粘在画布上
setTimeout(glitchImg, randInt(250, 1000));//随机延时执行glitchImg
}, 500);
};
var clear = function() {
context.clearRect(0, 0, canvas.width, canvas.height);
};
var glitchImg = function() {
for (var i = 0; i < randInt(1, 13); i++) {
var x = Math.random() * w;
var y = Math.random() * h;
var spliceWidth = w - x;//
var spliceHeight = randInt(5, h / 3);
context.drawImage(canvas, 0, y, spliceWidth, spliceHeight, x, y, spliceWidth, spliceHeight);
//将从（0，y）处剪切的图像附在画布的（x，y）中
context.drawImage(canvas, spliceWidth, y, x, spliceHeight, 0, y, x, spliceHeight);
//将从（spliceWidth,y）处剪切的图像附在画布（0,y）处。伸缩宽度在（0,w）,伸缩高度在（5，h/3）
}
};
var randInt = function(a, b) {
return ~~(Math.random() * (b - a) + a);
};
</script>
</body></html>
![图片描述][1]
