<!DOCTYPE html> <html> <head> <metacharset="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(){ varmoon=newImage(); 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 (vari=0;i<starCount;i++) { varstar=newStar(); star.init(); star.draw(); arr.push(star); } //画流星 for (vari=0;i<rainCount;i++) { varrain=newMeteorRain(); 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 (varn=0; n < starCount; n++){ arr[n].getColor(); arr[n].draw(); } setTimeout("playStars()",100); } /*流星雨开始*/ varMeteorRain=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 varx=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 varcos=Math.cos(this.angle*3.14/180); varsin=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(){ vara=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 varline=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 varx=this.x+this.width-this.offset_x; vary=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 (varn=0; n < rainCount; n++){ varrain=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> <styletype="text/css"> body{ background-color: black; } body,html{width:100%;height:100%;overflow:hidden;} </style> </head> <body> <canvasid="stars"></canvas> </body> </html> | 