Canvas引入跨域的图片导致toDataURL()报错的问题的解

                var c=document.getElementById("cover_show");
                var img=new Image();
                img.src="http://vsqx-cover-xxxxxx.coscd.myqcloud./"+this.vsqx_uid+".jpg";
                //增加这一行
                img.setAttribute("crossOrigin",'anonymous');
                img.onload = function(){
                    var cxt=c.getContext("2d");
                    cxt.drawImage(img,0,0,300,150,0,0,200,126);
                }