Canvas制作的粒子效果

2018-12-13 分类：Javascript 作者：huanggr 阅读（1107）

canvas可以当做画布去实现一些动画，比用css3来实现效果性能损耗要低，代码少，但是效果杠杠滴，接下来我们来看看

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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<meta name="keywords" content=""/>
<meta name="description" content=""/>
<style type="text/css">
* {
margin: 0;padding: 0;
}
html,body {
width: 100%;
height: 100%;
overflow: hidden;
}
canvas {
background: #000;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>

<script type="text/javascript">
var canvas = document.getElementById('canvas'),
c = canvas.getContext('2d'),
oW,
oH,
// 粒子的个数
count,
// 速度
speed = 5,
// 装粒子的数组
dotteds = [];

// 获取与设置宽高
function getAndSet(){
// 获取
oW = window.innerWidth || document.body.clientWidth;
oH = window.innerHeight || document.body.clientHeight;
// 设置
canvas.width = oW;
canvas.height = oH;

// 粒子的个数
count = Math.floor(oW * oH / 3000);
console.log(count);
}
getAndSet();
// 窗口大小改变
window.onresize = function(){
getAndSet();
}

// 生成粒子
for (var i = 0; i < count; i++) {
dotteds.push(new Dotted(i * Math.floor(Math.random() * 361)))
}

// 创建单个例子对象
function Dotted(hue){
// 单个例子的起始坐标
this.x = Math.random() * oW;
this.y = Math.random() * oH;
this.r = Math.random() * 3 + 1;

// 单个粒子的速度
this.vx = (Math.random()-0.5) * speed || 1;
this.vy = (Math.random()-0.5) * speed || 1;

// 颜色值
this.hue = hue;
}
// 粒子速度更新
Dotted.prototype.update = function(){
this.x += this.vx;
this.y += this.vy;

if (this.x < 0 || this.x > oW) {
this.vx *= -1;
this.r = Math.random() * 3 + 1;
this.hue = Math.floor(Math.random() * 361);
}
if (this.y < 0 || this.y > oH) {
this.vy *= -1;
this.r = Math.random() * 3 + 1;
this.hue = Math.floor(Math.random() * 361);
}
}

function move(){
window.requestAnimationFrame(move);

c.clearRect(0,0,oW,oH);
// c.fillStyle = 'rgba(0,0,0,.2)';
// c.fillRect(0,0,oW,oH);

for (var i = 0; i < dotteds.length; i++) {
var d = dotteds[i];
d.update();

c.beginPath();
c.arc(d.x,d.y,d.r,0,Math.PI*2,true);
c.fillStyle = 'hsl('+ d.hue +',50% , 50%)';
c.fill();
}
}
move();
</script>
</body>
</html>