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HTML5 canvas particles create the effect of snowy background

不言Original: 2018-08-31 11:42:301949browse

The content of this article is about the effect of html5 canvas particles forming a snowy background. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>canvas粒子形成下雪背景</title>
    body{
        margin: 0px;
        padding: 0px;
    }
    #canvas{
        display: block;
        background: #222;
    }
</style>
</head>
<body>
    <canvas id="canvas"></canvas>
</body>
<script>
    var canvas = document.getElementById("canvas");//获取canvas
    var ctx = canvas.getContext("2d");//创建画笔
    var w = canvas.width = window.innerWidth;//浏览器宽度
    var h = canvas.height = window.innerHeight;//浏览器高度
    window.onresize = function(){
        w = canvas.width = window.innerWidth;
        h = canvas.height = window.innerHeight;
    };//当浏览器刷新的时候刷新
    var num = 1000;//数量
    var shuju = [];//空数组
    for(i = 0;i<num;i++){
        shuju.push({//数组末项添加
            x : Math.random()*w, 
            y : Math.random()*h,
            r : Math.random()*2
        });
        draw(shuju[i].x,shuju[i].y,shuju[i].r)//for循环循环darw function
    };
    console.log(shuju[0]);

    function draw(x1,y1,r1){
        ctx.beginPath();//开始绘画
        ctx.fillStyle = "#fff";//颜色
        ctx.arc(x1,y1,r1,0,2*Math.PI,false)//arc园
        ctx.fill();//填充
    }

    function chageY(){
        for(var i = 0;i<num;i++){//for循环
            shuju[i].y += Math.random()*5;
            if(shuju[i].y > h){//大于高度
                shuju[i].y = 0;//等于0
            }
            draw(shuju[i].x,shuju[i].y,shuju[i].r);//调取
        }
    }

    setInterval(function(){
        ctx.clearRect(0,0,w,h);//清楚画布 0 0 高度 宽度
        chageY(); 
    },10);

</script>

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