js canvas实现星空连线背景特效
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<html>
<head>
<meta charset="UTF-8">
<title>canvas星空连线背景特效</title>
<style type="text/css">
body{
margin: 0;
}
#canvas{
display: block;
background: #000;
margin: 0 auto;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<script>
function Starry(){
this.cxt=canvas.getContext("2d");
canvas.width=window.innerWidth;
canvas.height=window.innerHeight;
this.cW=canvas.width;
this.cH=canvas.height;
this.num=200;
this.data=[];
}
Starry.prototype={
init: function(){
for (var i=0;i<this.num;i++) {
this.data[i]={
x:Math.random()*this.cW,
y:Math.random()*this.cH,
cX:Math.random()*0.6-0.3,
cY:Math.random()*0.6-0.3
};
this.drawCircle(this.data[i].x,this.data[i].y);
}
},
drawCircle: function(x,y){
var cxt=canvas.getContext("2d");
cxt.save();//保存路径
cxt.fillStyle="pink";
cxt.beginPath();//开始路径
cxt.arc(x,y,1,0,Math.PI*2,false);
cxt.closePath();//结束路径
cxt.fill();//填充方法
cxt.restore();//释放路径
},
drawLine: function(x1,y1,x2,y2){
var cxt=this.cxt;
var color=cxt.createLinearGradient(x1,y1,x2,y2);
color.addColorStop(0,"yellow");
color.addColorStop(1,"green");
cxt.save();
cxt.strokeStyle=color;
cxt.beginPath();//开始路径
cxt.moveTo(x1,y1);
cxt.lineTo(x2,y2);
cxt.closePath();//结束路径
cxt.stroke();//填充方法
cxt.restore();//释放路径
},
moveCircle: function(){
var self=this;
self.cxt.clearRect(0,0,self.cW,self.cH);
for(var i=0;i<self.num;i++){
self.data[i].x+=self.data[i].cX;
self.data[i].y+=self.data[i].cY;
if(self.data[i].x>self.cW||self.data[i].x<0){
self.data[i].cX=-self.data[i].cX;
}
if(self.data[i].x>self.cH||self.data[i].y<0){
self.data[i].cY=-self.data[i].cY;
}
this.drawCircle(self.data[i].x,self.data[i].y);
for(var j=i+1;j<self.num;j++){
if(Math.pow(self.data[i].x-self.data[j].x,2)
+Math.pow(self.data[i].y-self.data[j].y,2)
<=50*50){
self.drawLine(self.data[i].x,self.data[i].y,
self.data[j].x,self.data[j].y);
}
}
}
}
}
var starry=new Starry();
starry.init();
setInterval(function(){starry.moveCircle();},1);
</script>
</body>
</html>
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