一起來看流星雨
代碼如下：
var context;
var arr = new Array();
var starCount = 800;
var rains = new Array();
var rainCount =20;
//初始化畫布及context
function init(){
//獲取canvas
var stars = document.getElementById("stars");
windowWidth = window.innerWidth; //當(dāng)前的窗口的高度
stars.width=windowWidth;
stars.height=window.innerHeight;
//獲取context
context = stars.getContext("2d");
}
//創(chuàng)建一個星星對象
var Star = function (){
this.x = windowWidth * Math.random();//橫坐標(biāo)
this.y = 5000 * Math.random();//縱坐標(biāo)
this.text=".";//文本
this.color = "white";//顏色
//產(chǎn)生隨機(jī)顏色
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();
}
//繪制
this.draw=function(){
context.fillStyle=this.color;
context.fillText(this.text,this.x,this.y);
}
}
//畫月亮
function drawMoon(){
var moon = new Image();
moon.src = "./images/moon.jpg"
context.drawImage(moon,-5,-10);
}
//頁面加載的時候
window.onload = function() {
init();
//畫星星
for (var i=0;i
var star = new Star();
star.init();
star.draw();
arr.push(star);
}
//畫流星
for (var i=0;i
var rain = new MeteorRain();
rain.init();
rain.draw();
rains.push(rain);
}
drawMoon();//繪制月亮
playStars();//繪制閃動的星星
playRains();//繪制流星
}
//星星閃起來
function playStars(){
for (var n = 0; n < starCount; n++){?
arr[n].getColor();?
arr[n].draw();?
}?
setTimeout("playStars()",100);
}
/*流星雨開始*/
var MeteorRain = function(){
this.x = -1;
this.y = -1;
this.length = -1;//長度
this.angle = 30; //傾斜角度
this.width = -1;//寬度
this.height = -1;//高度
this.speed = 1;//速度
this.offset_x = -1;//橫軸移動偏移量
this.offset_y = -1;//縱軸移動偏移量
this.alpha = 1; //透明度
this.color1 = "";//流星的色彩
this.color2 = ""; //流星的色彩
/****************初始化函數(shù)********************/
this.init = function () //初始化
{
this.getPos();
this.alpha = 1;//透明度
this.getRandomColor();
//最小長度，最大長度
var x = Math.random() * 80 + 150;
this.length = Math.ceil(x);
// x = Math.random()*10+30;
this.angle = 30; //流星傾斜角
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 ; //流星所占寬度
this.height = this.length*sin ;//流星所占高度
this.offset_x = this.speed*cos ;
this.offset_y = this.speed*sin;
}
/**************獲取隨機(jī)顏色函數(shù)*****************/
this.getRandomColor = function (){
var a = Math.ceil(255-240* Math.random());?
//中段顏色
this.color1 = "rgba("+a+","+a+","+a+",1)";
//結(jié)束顏色
this.color2 = "black";
}
/***************重新計算流星坐標(biāo)的函數(shù)******************/
this.countPos = function ()//
{
//往左下移動,x減少，y增加
this.x = this.x - this.offset_x;
this.y = this.y + this.offset_y;
}
/*****************獲取隨機(jī)坐標(biāo)的函數(shù)*****************/
this.getPos = function () //
{
//橫坐標(biāo)200--1200
this.x = Math.random() * window.innerWidth; //窗口高度
//縱坐標(biāo)小于600
this.y = Math.random() * window.innerHeight; //窗口寬度
}
/****繪制流星***************************/
this.draw = function () //繪制一個流星的函數(shù)
{
context.save();
context.beginPath();
context.lineWidth = 1; //寬度
context.globalAlpha = this.alpha; //設(shè)置透明度
//創(chuàng)建橫向漸變顏色,起點(diǎn)坐標(biāo)至終點(diǎn)坐標(biāo)
var line = context.createLinearGradient(this.x, this.y,?
this.x + this.width,?
this.y - this.height);
//分段設(shè)置顏色
line.addColorStop(0, "white");
line.addColorStop(0.3, this.color1);
line.addColorStop(0.6, this.color2);
context.strokeStyle = line;
//起點(diǎn)
context.moveTo(this.x, this.y);
//終點(diǎn)
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);
//重新計算位置，往左下移動
this.countPos();
//透明度增加
this.alpha -= 0.002;
//重繪
this.draw();?
}
}
//繪制流星
function playRains(){
for (var n = 0; n < rainCount; n++){?
var rain = rains[n];
rain.move();//移動
if(rain.y>window.innerHeight){//超出界限后重來
context.clearRect(rain.x,rain.y-rain.height,rain.width,rain.height);
rains[n] = new MeteorRain();
rains[n].init();
}
}?
setTimeout("playRains()",2);
}
/*流星雨結(jié)束*/
body{
background-color: black;
}
body,html{width:100%;height:100%;overflow:hidden;}
這是轉(zhuǎn)的一個小哥哥的，原文網(wǎng)址：https://www.cnblogs.com/springcloud/p/8432806.html
