在上一篇的基础上
//流星
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 = 255 * Math.random();
a = Math.ceil(a);
var a1 = 255 * Math.random();
a1 = Math.ceil(a1);
var a2 = 255 * Math.random();
a2 = Math.ceil(a2);
//中段颜色
this.color1 = "rgba(" + a.toString() + "," + a1.toString() + "," + a2.toString() + ",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
var x = Math.random() * 1000 + 400;
this.x = Math.ceil(x);
x = Math.random() * 600;
//纵坐标小于600
this.y = Math.ceil(x);
}
/****绘制流星***************************/
this.draw = function () //绘制一个流星的函数
{
context.save();
context.beginPath();
context.lineWidth = 3;
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(0.1, 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();
}
}
该对象已自带绘制自己的方法，主要是设置渐变色，设置线宽，然后画一条线
还有移动的方法，就是做偏移，将偏移后的尾巴清除，再重绘
2、初始化若干个流星
在onload监听中加入：
//全局变量
var rains = new Array();
var rainCount = 20;
//onload监听中加入
//流星来了
for (var i=0;i
function playRains(){
for (var n = 0; n < rainCount; n++){
var rain = rains[n];
rain.move();//移动
if(rain.y>600){//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()",50);
}
然后在onload中加入代码：
playRains();
4、添加背景音乐
收工！！
