這里我截取的是一個(gè)圖片，實(shí)際上是會(huì)動(dòng)的。廢話不多說，上代碼。

HTML：



<canvas id="canvas"></canvas>

1

CSS：



/css reset /

body,p,div,ol,ul,li,dl,dt,dd,h1,h2,h3,h4,h5,h6,form,input,iframe,nav {

    margin: 0;

    padding: 0;

}

html,body {

    width: 100%;

    height: 100%;

}

body {

    font: 14px Microsoft YaHei;

    -webkit-text-size-adjust:100%;

    -moz-user-select: none;

    -webkit-user-select: none;

    user-select: none;

    position: relative;

    background: #000;

}

canvas {

    width: 100%;

    height: 100%;

    display: block;

    opacity: .8;

}





// 音量大小,0.01-1





//宇宙

var canvas = document.getElementById('canvas'),

ctx = canvas.getContext('2d'),

w = canvas.width = window.innerWidth,

h = canvas.height = window.innerHeight,



hue = 217,

stars = [],

count = 0,

maxStars = 1100;                //星星數(shù)量,默認(rèn)1300

var canvas2 = document.createElement('canvas'),

ctx2 = canvas2.getContext('2d');

canvas2.width = 100;

canvas2.height = 100;

var half = canvas2.width / 2,

gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);

gradient2.addColorStop(0.025, '#CCC');

gradient2.addColorStop(0.1, 'hsl(' + hue + ', 61%, 33%)');

gradient2.addColorStop(0.25, 'hsl(' + hue + ', 64%, 6%)');

gradient2.addColorStop(1, 'transparent');



ctx2.fillStyle = gradient2;

ctx2.beginPath();

ctx2.arc(half, half, half, 0, Math.PI 2);

ctx2.fill();



// End cache

function random(min, max) {

    if (arguments.length < 2) {

        max = min;

        min = 0;

    }



    if (min > max) {

        var hold = max;

        max = min;

        min = hold;

    }



    return Math.floor(Math.random() (max - min + 1)) + min;

}



function maxOrbit(x, y) {

    var max = Math.max(x, y),

    diameter = Math.round(Math.sqrt(max max + max max));

    return diameter / 2;

    //星星移動(dòng)范圍，值越大范圍越小，

}



var Star = function() {



    this.orbitRadius = random(maxOrbit(w, h));

    this.radius = random(60, this.orbitRadius) / 10;       //星星大小,值越大星星越小,默認(rèn)8

    

    this.orbitX = w / 2;

    this.orbitY = h / 2;

    this.timePassed = random(0, maxStars);

    this.speed = random(this.orbitRadius) / 80000;        //星星移動(dòng)速度,值越大越慢,默認(rèn)5W

    

    this.alpha = random(2, 10) / 10;



    count++;

    stars[count] = this;

}



Star.prototype.draw = function() {

    var x = Math.sin(this.timePassed) this.orbitRadius + this.orbitX,

    y = Math.cos(this.timePassed) this.orbitRadius + this.orbitY,

    twinkle = random(10);



    if (twinkle === 1 && this.alpha > 0) {

        this.alpha -= 0.05;

    } else if (twinkle === 2 && this.alpha < 1) {

        this.alpha += 0.05;

    }



    ctx.globalAlpha = this.alpha;

    ctx.drawImage(canvas2, x - this.radius / 2, y - this.radius / 2, this.radius, this.radius);

    this.timePassed += this.speed;

}



for (var i = 0; i < maxStars; i++) {

    new Star();

}



function animation() {

    ctx.globalCompositeOperation = 'source-over';

    ctx.globalAlpha = 0.5;                                 //尾巴

    ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 2)';

    ctx.fillRect(0, 0, w, h)



    ctx.globalCompositeOperation = 'lighter';

    for (var i = 1,

    l = stars.length; i < l; i++) {

        stars[i].draw();

    };



    window.requestAnimationFrame(animation);

}



animation();

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