今天，我们继续分享 JavaScript 实现的效果例子，这篇文章会介绍使用 JavaScript 实现水波纹效果。水波效果以图片为背景，点击图片任意位置都会触发。有时候，我们使用普通的 Javascript 就可以创建一个很有趣的解决功能。 
源码下载
Step 1. HTML
和以前一样，首先是 HTML 代码：
<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Water drops effect</title>
<link rel=”stylesheet” href=”css/main.css” type=”text/css” />
<script src=”js/vector2d.js” type=”text/javascript” charset=”utf-8″></script>
<script src=”js/waterfall.js” type=”text/javascript” charset=”utf-8″></script>
</head>
<body>
<div class=”example”>
<h3><a href=”#”>Water drops effect</a></h3>
<canvas id=”water”>HTML5 compliant browser required</canvas>
<div id=”switcher”>
<img onclick=’watereff.changePicture(this.src);’ src=”data_images/underwater1.jpg” />
<img onclick=’watereff.changePicture(this.src);’ src=”data_images/underwater2.jpg” />
</div>
<div id=”fps”></div>
</div>
</body>
</html>
Step 2. CSS
这是用到的 CSS 代码：
body{background:#eee;margin:0;padding:0}
.example{background:#FFF;width:600px;border:1px #000 solid;margin:20px auto;padding:15px;-moz-border-radius: 3px;-webkit-border-radius: 3px}
#water {
width:500px;
height:400px;
display: block;
margin:0px auto;
cursor:pointer;
}
#switcher {
text-align:center;
overflow:hidden;
margin:15px;
}
#switcher img {
width:160px;
height:120px;
}
Step 3. JS
下面是主要的 JavaScript 代码：
function drop(x, y, damping, shading, refraction, ctx, screenWidth, screenHeight){
this.x = x;
this.y = y;
this.shading = shading;
this.refraction = refraction;
this.bufferSize = this.x * this.y;
this.damping = damping;
this.background = ctx.getImageData(0, 0, screenWidth, screenHeight).data;
this.imageData = ctx.getImageData(0, 0, screenWidth, screenHeight);
this.buffer1 = [];
this.buffer2 = [];
for (var i = 0; i < this.bufferSize; i++){
this.buffer1.push(0);
this.buffer2.push(0);
}
this.update = function(){
for (var i = this.x + 1, x = 1; i < this.bufferSize – this.x; i++, x++){
