star rain

<!DOCTYPE html>
<html>
<head><meta charset="utf-8"><title>流星雨</title><script>var context;var arr = new Array();var starCount = 800;var rains = new Array();var rainCount = 20;function init() {var stars = document.getElementById("stars");windowWidth = window.innerWidth; //当前的窗口的高度stars.width = windowWidth;stars.height = window.innerHeight;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--1200this.x = Math.random() * window.innerWidth; //窗口高度
//纵坐标小于600this.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"></canvas>
</body>
</html>
star rain

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