canvas 弹幕效果（实例分享）

话不多说，请看代码

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Document</title>
</head>
<body>
 <canvas style="width: 1280px;height: 720px;background-color: rgba(0,0,0,0.2)">你的浏览器不支持canvas</canvas>
</body>
<script src="http://www.jq22.com/jquery/jquery-1.10.2.js"></script>
<script>
 (function ($) {
 function Barrager(dom) {
 this.canvas = dom.get(0);
 this.ctx = this.canvas.getContext("2d");
 this.msgs = new Array(300);//缓冲池，长度越大，屏幕上显示的就越多
 this.width = 1280;//canvas分辨率1280*720
 this.height = 720;
 this.canvas.width=this.width;//上边的两步可以省略，直接在这里赋值
 this.canvas.height=this.height;
 this.font = "30px 黑体";//字体和字体大小
 this.ctx.font=this.font;
 //颜色数组，在绘制过程中随机从这里取出颜色
 this.colorArr=["Olive","OliveDrab","Orange","OrangeRed","Orchid","PaleGoldenRod","PaleGreen","PaleTurquoise","PaleVioletRed","PapayaWhip","PeachPuff","Peru","Pink","Plum","PowderBlue","Purple","Red","RosyBrown","RoyalBlue","SaddleBrown","Salmon","SandyBrown","SeaGreen","SeaShell","Sienna","Silver","SkyBlue"];
 this.interval = "";
 this.draw = function () {//绘制方法
  if (this.interval != "")return;
  var _this=this;
  this.interval = setInterval(function () {//每隔20毫秒重新绘制一次，间隔最好小于40，要不然效果就跟播放图片差不多
  //1，清除屏幕
  _this.ctx.clearRect(0, 0, _this.width, _this.height);
  _this.ctx.save();
  //2，循环缓冲区域，把没有设置Left，Top，Speed，Color先赋值，赋值的就改变left值（产生移动效果），left值小于200就会从缓冲区移除
  for (var i = 0; i < _this.msgs.length; i++) {
   if (!(_this.msgs[i] == null || _this.msgs[i] == "" || typeof(_this.msgs[i]) == "undefined")) {
   if(_this.msgs[i].L==null || typeof(_this.msgs[i].L)=="undefined"){
    _this.msgs[i].L=_this.width;
    _this.msgs[i].T=parseInt(Math.random() * 700);
    _this.msgs[i].S=parseInt(Math.random() * (10 - 4) + 4);
    _this.msgs[i].C=_this.colorArr[Math.floor(Math.random() * _this.colorArr.length)];
   }else{
    if(_this.msgs[i].L<-200){
    _this.msgs[i]=null;
    }else {
    _this.msgs[i].L=parseInt(_this.msgs[i].L-_this.msgs[i].S);
    _this.ctx.fillStyle =_this.msgs[i].C;
    _this.ctx.fillText(_this.msgs[i].msg,_this.msgs[i].L,_this.msgs[i].T);
    _this.ctx.restore();
    }
   }
   }
  }
  }, 20);
 };
 //添加数据，数据格式[{"msg":"nihao"}]
 this.putMsg = function (datas) {//循环缓冲区，把位置是空的装填上数据
  for (var j = 0; j < datas.length; j++) {
  for (var i = 0; i < this.msgs.length; i++) {
   if (this.msgs[i] == null || this.msgs[i] == "" || typeof(this.msgs[i]) == "undefined") {
   this.msgs[i] = datas[j];
   break;
   }
  }
  }
  this.draw();
 };
 this.clear = function () {//清除定时器，清除屏幕，清空缓冲区
  clearInterval(this.interval);
  this.interval="";
  this.ctx.clearRect(0, 0, this.width, this.height);
  this.ctx.save();
  for(var i=0;i<this.msgs.length;i++){
  this.msgs[i]=null;
  }
 };
 }
 $.fn.barrager = function (para) {
 if (typeof(para)=="string") {
  try{
  var api = $(this).data('barrager_api');
  api[para].apply(api);
  }catch (e){}
 } else if (typeof para == 'object' || !para) {
  $this = $(this);
  if ($this.data('barrager_api') != null && $this.data('barrager_api') != ''){
  var api = $this.data('barrager_api');
  api.putMsg(para);
  }else{
  var api = new Barrager($this);
  $this.data('barrager_api', api);
  api.putMsg(para);
  }
 } else {
  $.error('Method ' + method + ' does not exist on jQuery.slidizle');
 }
 return this;
 }
})(jQuery);
</script>
<script>
 // $('canvas').barrager([{"msg":"这是我发的。。。哈哈哈"}]);// 发送弹幕

 $('canvas').barrager([{"msg":"看着不错。。。。"},{"msg":"哈哈哈。。。。"},{"msg":"不错不错。。"},{"msg":"真好看。。。。"}]);//多条发送方式

 // $('canvas').barrager("clear"); //清除/关闭弹幕
</script>
</html>

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