javascript - 看看哪里的bug？-PHP中文网问答

<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>LTR</title>
<script src="easeljs-0.8.2.min.js"></script>
<style>
body,html{width:100%;height:100%;margin:0;padding:0}
#canvas{background:#000;}
</style>
</head>
<body>
<img src="title.png" alt="tulip" id="tulip" style="display:none;width:100%;height:30%" />
<canvas id="canvas" ></canvas>
<script>

      var canvas;
      var stage;
      var img2 = new Image();
      var sprite;
      
      var canvas=document.getElementById("canvas");
      var ctx=canvas.getContext("2d");
      var img=document.getElementById("tulip");
      document.getElementById("tulip").onload=function(){
      canvas.width  =     img.width;
      canvas.height = img.height;
      var i = 0;
      var timer = setInterval(function(){          
          if(i < img.width){
                i += 10;
                ctx.drawImage(img,0,0, i,img.height,0,0,i,img.height);
                addS(Math.random()* 5 + 10 , i-10,-img.height , 0.1);
              }else{clearInterval(timer);}
          },100);
        };

        stage = new  createjs.Stage(canvas);
        var data = {
            images: ["star.png"],
            frames:{width:23,height:23,regX:0,regY:0},
            }
            sprite = new createjs.Sprite(new createjs.SpriteSheet(data));
            createjs.Ticker.setFPS(20);
            createjs.Ticker.addEventListener("tick" , tick);
      function tick(e){
        var t= stage.getNumChildren();
        for(var i = t-1 ; i >0 ; i--){
          var s = stage.getChildAt(i);
          s.vY += 2;
          s.vX += 1;
          s.x += s.vX;
          s.y += s.vY;
          s.scaleX = s.scaleY = s.scaleX + s.vS;
          s.alpha += s.vA;
          if(s.alpha <= 0 || s.y > canvas.height){
            stage.removeChildAt(i);
             }
          }
            stage.update(e);
          }
          function addS(count , x , y , speed){
                for(var i = 0 ; i < count ; i++){
                    var s = sprite.clone();
                    s.x = x;
                    s.y = y;
                    s.alpha = Math.random() * 0.5 + 0.5;
                    s.scaleX = s.scaleY = Math.random() + 0.3;
                    var  a = Math.PI * 2 * Math.random();
                    var  v = (Math.random() -  0.5) * 30 * speed  ;
                    s.vX = Math.cos(a) * v;
                    s.vY = Math.sin(a) * v;
                    s.vS = (Math.random() - 0.5) * 0.2;
                    s.vA = -Math.random() * 0.05 - 0.01;
                    stage.addChild(s);
                }
          }

</script>
</body>
</html>
代码的其中一张图片频闪，是什么问题。怎么解决？
想要的效果是：图片title.png在drawImage的同时伴有star.png的出现。。