》》星空背景

<!DOCTYPE html>
<html>

    <head lang="en">
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="renderer" content="webkit" />
        <meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0" />
        <title>星空背景</title>
        <link rel="stylesheet" href="css/bootstrap.min.css" />
    </head>
    <!--[if lt IE 9]>
      <script src="https://cdn.bootcss.com/html5shiv/3.7.3/html5shiv.min.js"></script>
      <script src="https://cdn.bootcss.com/respond.js/1.4.2/respond.min.js"></script>
    <![endif]-->

    <body>

        <canvas id="canvas" width="1920" height="960">
            
        
        <div class="clearfix"></div>
        <div id="ee" style="width: 100px;height: 100px;background-color: red;border: 1px solid darkorange;z-index: -1;">
            
        </div>
        </canvas>
    </body>
    <script type="text/javascript" src="js/jquery-1.12.4.min.js"></script>

    <script>
        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 = 1200;

        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, '#fff');
        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();

        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;
        }

        var Star = function() {

            this.orbitRadius = random(maxOrbit(w, h));
            this.radius = random(60, this.orbitRadius) / 12;
            this.orbitX = w / 2;
            this.orbitY = h / 2;
            this.timePassed = random(0, maxStars);
            this.speed = random(this.orbitRadius) / 900000;
            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 = 0.8;
            ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 1)';
            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();
    </script>

</html>
posted on 2017-12-06 19:24 风过无涟漪阅读(272) 评论(0) 收藏举报