canvas之背景特效

2018-06-24 02:07:56来源：未知阅读 ()

需具备js基础知识以及canvas相关方法(可查阅相关文档)

下面是一篇有关js与canvas的背景特效

基于面向过程的思维

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        #canvas {
            display: block;
            background: #000;
        }
    </style>
</head>
<body>
    <canvas id="canvas"></canvas>
    <script>
        window.requestAnimationFrame =(function(){//解决定时器卡问题，使用帧动画
            return window.requestAnimationFrame ||
                    window.webkitRequestAnimationFrame ||
                    window.mozRequestAnimationFrame ||
                    function(callback){
                        window.setInterval (callback,1000/60);
                    };
        })();
        //初始化变量
        var canv=document.getElementsByName("canvas");
        var cxt=canvas.getContext("2d");
        var w,h;
        var num=200;
        var data=[];
        var move={};
        window.onresize=init;//在浏览器窗口变化时重置
        init();
        //获取浏览器宽高并使粒子随机分布
        function init(){
            canvas.width = window.innerWidth ;
            canvas.height = window.innerHeight ;
            w = canvas.width;
            h = canvas.height;
            for(var i=0;i<num;i++){
                data[i]={x:Math.random()*w,y:Math.random()*h,cX:Math.random()*0.6-0.3,cY:Math.random()*0.6-0.3};
                Cricle(data[i].x,data[i].y);
            }
        }
        //绘制粒子
        function Cricle(x,y){
            cxt.save();
            cxt.fillStyle ="pink";
            cxt.beginPath ();
            cxt.arc (x,y,0.5,Math.PI*2,false);
            cxt.closePath ();
            cxt.fill ();
            cxt.restore ();
        }
        //自执行使粒子运动
        !function draw(){
            cxt.clearRect(0,0,w,h);//清除，防止粒子运动成线
            for(var i=0;i<num;i++){
                data[i].x+=data[i].cX;//粒子运动
                data[i].y+=data[i].cY;
                if(data[i].x>w||data[i].x<0) data[i].cX=-data[i].cX;//设置边界值判断防止粒子跑出边界
                if(data[i].y>h||data[i].y<0) data[i].cY=-data[i].cY;
                Cricle(data[i].x,data[i].y);
                for(var j=i+1;j<num;j++){
                    //使粒子连线
                    if((data[i].x-data[j].x)*(data[i].x-data[j].x)+(data[i].y-data[j].y)*(data[i].y-data[j].y)<=50*50){
                        line(data[i].x,data[i].y,data[j].x,data[j].y,false);
                    }
                    //使粒子与鼠标连线
                    if(move.x){
                        if((data[i].x-move.x)*(data[i].x-move.x)+(data[i].y-move.y)*(data[i].y-move.y)<=100*100){
                            line(data[i].x,data[i].y,move.x,move.y,true);
                        }
                    }
                }
            }
            window.requestAnimationFrame(draw);//定时器
//            setInterval(function(){
//                draw();
//            },130);
        }();
        //使粒子的连线颜色渐变
        function line(x1,y1,x2,y2,isMove){
            var color=cxt.createLinearGradient(x1,y1,x2,y2);
            if(!isMove){
                color.addColorStop(0,"yellow");
                color.addColorStop(1,"pink");
            }else{
                color.addColorStop(0,"#fff");
                color.addColorStop(1,"#0bd2dd");
            }
            cxt.save();
            cxt.strokeStyle=color;
            cxt.beginPath();
            cxt.moveTo(x1,y1);
            cxt.lineTo(x2,y2);
            cxt.stroke();
            cxt.restore();
        }
        //鼠标移入与粒子连线
        document.onmousemove=function(e){
            move.x= e.clientX;
            move.y= e.clientY;
        }
    </script>
</body>
</html>