var reader = new FileReader();
                    reader.onload = function (e) {
                        //图片base64数据
                        var imgBase64Data = e.target.result;
                        var pos = imgBase64Data.indexOf("4")+2;
                        imgBase64Data = imgBase64Data.substring(pos, imgBase64Data.length - pos);//去掉Base64:开头的标识字符
                        $.ajax({
                            type: "POST",
                            url: "http://imginapi.com/image/AddImage",
                            async: false,
                            xhrFields: { withCredentials: true },
                            data: { 'base64StrImgData': imgBase64Data, 'imgFormat':  fileext},
                            dataType: "text",
                            success: function (data) {
                                alert(data);
                               domUtils.on(iframe, 'load', callback);
                            },

                            error: function (err) {
                                alert("error");
                                alert(err.responseText);
                            }

                        });
                        return;

                    };
                    reader.readAsDataURL(input.files[0]);

/// <summary>  
        /// 图像转换为Base64编码  
        /// </summary>  
        /// <param name="image">图像</param>  
        /// <param name="format">图像格式</param>  
        /// <param name="throwException">出现异常时是否抛出</param>
        /// <returns>转换成功返回其Base64编码；失败返回空串</returns>  
        public static string ImageToBase64(System.Drawing.Image image, ImageFormat format, OPResult opRes, bool throwException = false)
        {
            return ExceptionHelper.ExceptionRecord(() =>
            {
                string base64String = "";
                try
                {
                    using (MemoryStream ms = new MemoryStream())
                    {
                        image.Save(ms, format);
                        byte[] imageBytes = ms.ToArray();
                        base64String = Convert.ToBase64String(imageBytes);
                    }
                }
                catch (Exception ex)
                {
                    throw new Exception("将图片转成base64字符串时出现异常:" + ex);
                }

                return base64String;
            }, opRes, throwException);
        }