流星雨网页特效

admin · 发表于 2022-5-28 20:10:06

[mw_shl_code=html,true]<!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--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"></canvas>
            </body>
            </html>[/mw_shl_code]

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