readLocalFile: function (index) {
                let reader = new FileReader();
                var localFile = document.getElementById("uploadFile_"+ index).files[0];
                var content;
                var current=this;
                reader.readAsDataURL(localFile,"UTF-8");   //必须放在前面
                reader.onload = function(event)
                    {
                        content = event.target.result;
                   var img = new Image();
                   img.src = content;
                   img.onload = function ()
                   {
                       var canvas = document.getElementById("canvasid");
                       var ctx = canvas.getContext("2d");
                       var hanzi = canvas.getContext("2d");
                       //图片下载完毕时异步调用callback函数。
                       ctx.drawImage(img, 0, 0, 300, 300);  //圖片
                       hanzi.font = "29px 微软雅黑";
                       hanzi.fillStyle = "#ff9900";
                       hanzi.translate(50,100);
                       hanzi.rotate( 315* Math.PI/180);
                       //获取地点 时间 账户
                       var dataa=new Date();
                       hanzi.fillText(dataa.getFullYear()+"/"+(dataa.getMonth()+1)+"/"+dataa.getDate(),10,30);                        
                       hanzi.fillText( sessionStorage.getItem("users"),10,70); //用户信息
                       //获取当前位置
                      var sssss= canvas.toDataURL("image/png");
                       current.imgs[index].push(sssss);  //获取图片base64代
                       hanzi.rotate( 45* Math.PI/180);
                       hanzi.translate(-50, -100);
                   };
            }