H5 canvas流星雨星星特效

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html 代码

<!DOCTYPE html>
<!– saved from url=(0065)http://www.17sucai.com/preview/537573/2016-08-18/star1/index.html –>
<html>
<head>
    <meta http-equiv=”Content-Type” content=”text/html; charset=UTF-8″>
    <title>一起来看流星雨</title>
    <script>
        var context;
        var arr = new Array();
        var starCount = 800;
        var rains = new Array();
        var rainCount = 20;
        //初始化画布及context
        function init() {
            //获取canvas
            var stars = document.getElementById(“stars”);
            windowWidth = window.innerWidth; //当前的窗口的高度
            stars.width = windowWidth;
            stars.height = window.innerHeight;
            //获取context
            context = stars.getContext(“2d”);
        }
        //创建一个星星对象
        var Star = function () {
            this.x = windowWidth * Math.random();//横坐标
            this.y = 5000 * Math.random();//纵坐标
            this.text = “.”;//文本
            this.color = “white”;//颜色
            //产生随机颜色
            this.getColor = function () {
                var _r = Math.random();
                if (_r < 0.5) {
                    this.color = “#333”;
                } else {
                    this.color = “white”;
                }
            }
            //初始化
            this.init = function () {
                this.getColor();
            }
            //绘制
            this.draw = function () {
                context.fillStyle = this.color;
                context.fillText(this.text, this.x, this.y);
            }
        }
        //画月亮
        function drawMoon() {
            var moon = new Image();
            moon.src = “./images/moon.jpg”
            context.drawImage(moon, -5, -10);
        }
        //页面加载的时候
        window.onload = function () {
            init();
            //画星星
            for (var i = 0; i < starCount; i++) {
                var star = new Star();
                star.init();
                star.draw();
                arr.push(star);
            }
            //画流星
            for (var i = 0; i < rainCount; i++) {
                var rain = new MeteorRain();
                rain.init();
                rain.draw();
                rains.push(rain);
            }
            drawMoon();//绘制月亮
            playStars();//绘制闪动的星星
            playRains();//绘制流星
        }
        //星星闪起来
        function playStars() {
            for (var n = 0; n < starCount; n++) {
                arr[n].getColor();
                arr[n].draw();
            }
            setTimeout(“playStars()”, 100);
        }
        /*流星雨开始*/
        var MeteorRain = function () {
            this.x = -1;
            this.y = -1;
            this.length = -1;//长度
            this.angle = 30; //倾斜角度
            this.width = -1;//宽度
            this.height = -1;//高度
            this.speed = 1;//速度
            this.offset_x = -1;//横轴移动偏移量
            this.offset_y = -1;//纵轴移动偏移量
            this.alpha = 1; //透明度
            this.color1 = “”;//流星的色彩
            this.color2 = “”; //流星的色彩
            /****************初始化函数********************/
            this.init = function () //初始化
            {
                this.getPos();
                this.alpha = 1;//透明度
                this.getRandomColor();
                //最小长度,最大长度
                var x = Math.random() * 80 + 150;
                this.length = Math.ceil(x);
                // x = Math.random()*10+30;
                this.angle = 30; //流星倾斜角
                x = Math.random() + 0.5;
                this.speed = Math.ceil(x); //流星的速度
                var cos = Math.cos(this.angle * 3.14 / 180);
                var sin = Math.sin(this.angle * 3.14 / 180);
                this.width = this.length * cos; //流星所占宽度
                this.height = this.length * sin;//流星所占高度
                this.offset_x = this.speed * cos;
                this.offset_y = this.speed * sin;
            }
            /**************获取随机颜色函数*****************/
            this.getRandomColor = function () {
                var a = Math.ceil(255 – 240 * Math.random());
                //中段颜色
                this.color1 = “rgba(” + a + “,” + a + “,” + a + “,1)”;
                //结束颜色
                this.color2 = “black”;
            }
            /***************重新计算流星坐标的函数******************/
            this.countPos = function ()//
            {
                //往左下移动,x减少,y增加
                this.x = this.x – this.offset_x;
                this.y = this.y + this.offset_y;
            }
            /*****************获取随机坐标的函数*****************/
            this.getPos = function () //
            {
                //横坐标200–1200
                this.x = Math.random() * window.innerWidth; //窗口高度
                //纵坐标小于600
                this.y = Math.random() * window.innerHeight; //窗口宽度
            }
            /****绘制流星***************************/
            this.draw = function () //绘制一个流星的函数
            {
                context.save();
                context.beginPath();
                context.lineWidth = 1; //宽度
                context.globalAlpha = this.alpha; //设置透明度
                //创建横向渐变颜色,起点坐标至终点坐标
                var line = context.createLinearGradient(this.x, this.y,
                    this.x + this.width,
                    this.y – this.height);
                //分段设置颜色
                line.addColorStop(0, “white”);
                line.addColorStop(0.3, this.color1);
                line.addColorStop(0.6, this.color2);
                context.strokeStyle = line;
                //起点
                context.moveTo(this.x, this.y);
                //终点
                context.lineTo(this.x + this.width, this.y – this.height);
                context.closePath();
                context.stroke();
                context.restore();
            }
            this.move = function () {
                //清空流星像素
                var x = this.x + this.width – this.offset_x;
                var y = this.y – this.height;
                context.clearRect(x – 3, y – 3, this.offset_x + 5, this.offset_y + 5);
                // context.strokeStyle=”red”;
                // context.strokeRect(x,y-1,this.offset_x+1,this.offset_y+1);
                //重新计算位置,往左下移动
                this.countPos();
                //透明度增加
                this.alpha -= 0.002;
                //重绘
                this.draw();
            }
        }
        //绘制流星
        function playRains() {
            for (var n = 0; n < rainCount; n++) {
                var rain = rains[n];
                rain.move();//移动
                if (rain.y > window.innerHeight) {//超出界限后重来
                    context.clearRect(rain.x, rain.y – rain.height, rain.width, rain.height);
                    rains[n] = new MeteorRain();
                    rains[n].init();
                }
            }
            setTimeout(“playRains()”, 2);
        }
/*流星雨结束*/
    </script>
    <style type=”text/css”>
        body {
            background-color: black;
        }
        body,
        html {
            width: 100%;
            height: 100%;
            overflow: hidden;
        }
    </style>
</head>
<body>
    <canvas id=”stars” width=”1920″ height=”847″></canvas>
</body>
</html>

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评论 4

  1. #1

    mmnghm

    匿名2年前 (2018-09-08)回复
  2. #2

    作者写的很好,基本copy就行了,但是setTimeout需要改为setInterval,另外我按照自己的写法改写了一下,欢迎查看,附链接:https://juejin.im/post/5c5fb457f265da2de52d6695

    匿名1年前 (2019-02-10)回复
    • 谢谢,欢迎常交流

      前端开发者1年前 (2019-02-17)回复
  3. #3

    we

    匿名1年前 (2019-02-10)回复