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Canvas 绘制粒子动画背景

<canvas id="canvas">您的浏览器不支持,请升级最新的版本!</canvas>
*{
margin:0px;
padding:0px;
}
body{
background:#000;
}
canvas{
position:absolute;
width:100%;
height:100%;
}
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 : 100,//粒子距离鼠标点的距离
array : []//保存n个圆形粒子对象
}
//创建随即颜色值
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;
}
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