Canvas 绘制粒子动画背景

效果如下：

代码如下：

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Title</title>
</head>
<style>
 *{
  margin:0px;
  padding:0px;
 }
 body{
  background:#000;
 }
 canvas{
  position:absolute;
  width:100%;
  height:100%;
 }
</style>
<body>
<canvas id="canvas">您的浏览器不支持，请升级最新的版本!</canvas>
<script>window.requestAnimFrame = ( function() {
 return window.requestAnimationFrame ||
   window.webkitRequestAnimationFrame ||
   window.mozRequestAnimationFrame ||
   function( callback ) {
    window.setTimeout( callback, 1000 / 60 );
   };
})();
var can = document.getElementById("canvas");
var cxt = can.getContext("2d");
can.width = window.innerWidth;
can.height = window.innerHeight;
cxt.lineWidth = 0.3;
//初始链接线条显示位置
var mousePosition = {
 x : 30*can.width/100,
 y : 30*can.height/100
}
//圆形粒子对象参数
var dots = {
 n : 500,//圆形粒子个数
 distance : 50,//圆形粒子之间的距离
 d_radius : 80,//粒子距离鼠标点的距离
 array : []//保存n个圆形粒子对象
}
//创建随机颜色值
function colorValue(min){
 return Math.floor(Math.random()*255 + min);
}
function createColorStyle(r,g,b){
 return "rgba("+r+","+g+","+b+", 1)";
}
//混合两个圆形粒子的颜色
function mixConnect(c1,r1,c2,r2){//圆的颜色 半径
 return (c1*r1+c2*r2)/(r1+r2);
};
//生成线条的颜色
function lineColor(dot1,dot2){//获取具体的圆的颜色再计算
 var color1 = dot1.color,
   color2 = dot2.color;
 var r = mixConnect(color1.r,dot1.radius,color2.r,dot2.radius);
 var g = mixConnect(color1.g,dot1.radius,color2.g,dot2.radius);
 var b = mixConnect(color1.b,dot1.radius,color2.b,dot2.radius);
 return createColorStyle(Math.floor(r),Math.floor(g),Math.floor(b));
}
//生成圆形粒子的颜色对象
function Color(min){
 min = min || 0;
 this.r = colorValue(min);
 this.g = colorValue(min);
 this.b = colorValue(min);
 this.style = createColorStyle(this.r,this.g,this.b);
}
//创建圆形粒子对象
function Dot(){
 //圆形粒子随机圆心坐标点
 this.x = Math.random()*can.width;
 this.y = Math.random()*can.height;
 //x y 方向运动的速度值
 this.vx = -0.5 + Math.random();
 this.vy = -0.5 + Math.random();
 this.radius = Math.random()*5;
 //this.color = "#ff3333";
 this.color = new Color();
}
//绘制出圆形粒子
Dot.prototype.draw = function(){
 cxt.beginPath();
 cxt.fillStyle = this.color.style;
 cxt.arc(this.x,this.y,this.radius,0,Math.PI*2,false);
 cxt.fill();
}
//添加圆形粒子
function createCircle(){
 for (var i=0;i<dots.n ;i++ )
 {
  dots.array.push(new Dot());
 }
}
//绘制出圆形粒子
function drawDots(){
 for (var i=0;i<dots.n ;i++ )
 {
  var dot = dots.array[i];
  dot.draw();
 }
}
//drawDots();
//移动
function moveDots(){
 for (var i=0;i<dots.n ;i++ ){
  var dot = dots.array[i];
  //当圆形粒子对象碰壁的时候就反弹回来
  if (dot.y < 0 || dot.y > can.height)
  {
   dot.vx = dot.vx;
   dot.vy = -dot.vy;
  }else if (dot.x < 0 || dot.x > can.width)
  {
   dot.vx = -dot.vx;
   dot.vy = dot.vy;
  }
  //给圆形粒子圆心坐标加上速度值移动圆形粒子
  dot.x += dot.vx;
  dot.y += dot.vy;
 }
}
//链接粒子对象
function connectDots(){
 for (var i=0;i<dots.n ; i++)
 {
  for ( var j=0;j<dots.n ; j++)
  {
   iDot = dots.array[i];
   jDot = dots.array[j];
   if ((iDot.x - jDot.x) < dots.distance && (iDot.y - jDot.y) < dots.distance && (iDot.x - jDot.x) > -dots.distance && (iDot.y - jDot.y) > -dots.distance)
   {
    if ((iDot.x - mousePosition.x) < dots.d_radius && (iDot.y - mousePosition.y) < dots.d_radius && (iDot.x - mousePosition.x) > -dots.d_radius && (iDot.y - mousePosition.y) > -dots.d_radius)
    {
     cxt.beginPath();
     //cxt.strokeStyle = "yellow";
     cxt.strokeStyle = lineColor(iDot,jDot);
     cxt.moveTo(iDot.x,iDot.y);
     cxt.lineTo(jDot.x,jDot.y);
     cxt.closePath();
     cxt.stroke();
    }
   }
  }
 }
}
createCircle();
//让圆形粒子不断的移动
function animateDots(){
 cxt.clearRect(0,0,can.width,can.height);
 moveDots();
 connectDots()
 drawDots();
 requestAnimFrame(animateDots);
}
animateDots();
can.onmousemove = function(ev){
 var ev = ev || window.event;
 mousePosition.x = ev.pageX;
 mousePosition.y = ev.pageY;
}
can.onmouseout = function(){
 mousePosition.x = can.width/2;
 mousePosition.y = can.height/2;
}
</script>
</body>
</html>

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