C#保存Base64格式图片

 .前端页面代码
 /**
 * 通过图片本地路径获取图片真实大小，并进行压缩
 */
 function getLocalRealSize(path, callback) {
     var img = new Image();
     var tempimg = new Image();
     img.src = path;
     img.onload = function() {
         var height = img.naturalHeight;
         var width = img.naturalWidth;
         img.width = img.naturalWidth;
         img.height = img.naturalHeight;
         //压缩图片
         var canvas = compressImage(img);
         tempimg = canvas.toDataURL('image/jpeg');

         callback(tempimg);
     }
 };
 /**
 * 压缩图片
 */
 function compressImage(image) {
         var canvas = document.createElement("canvas");
         var mwidth = image.width;
         var mheight = image.height;
         var scale = ;
         var i = ;
         while (true) {
             if (mwidth >> i <=  && mheight >> i <= ) {
                 scale = Math.pow(0.5, i);
                 break;
             }
             i += ;
         }
         canvas.width = mwidth * scale;
         canvas.height = mheight * scale;
         canvas.getContext("2d").drawImage(image, , , mwidth * scale, mheight * scale);
         return canvas;
     }
     //主页面   车主首页    跳转
     document.getElementById("driverindex").addEventListener("tap", function() {
         //获取img对象
         var OwerImg = document.getElementById("owner-photo-img");
         var OwerCardImg = document.getElementById("owner-cardphoto-img");
         var OwerLicenceImg = document.getElementById("owner-driver1-img");
         var OwerDrivingLicenceImg = document.getElementById("owner-driver2-img");
         var CarImg = document.getElementById("owner-car-img");
         var AssuranceImg = document.getElementById("owner-sure-img");

         var oArray=source.split("|");
         var totalCount=imgCount+oArray.length-;
         if(totalCount<){
             mui.toast("请上传完整信息");
             return false;
         }
         uploadImg();
     });
 });
 // 上传文件
 var uploadImg = function() {
     var server = imgUrl+'/clientapi/driver/ApplayCertification';
     //outSet("开始上传：")
     var wt = plus.nativeUI.showWaiting();
     var task = plus.uploader.createUpload(server, {
             method: "POST",
             blocksize: ,
             priority:
         },
         function(t, status) { //上传完成
             if (t.state ==  && status == ) {
                 wt.close();
                 //outLine("上传成功：" + t.responseText);
                 //上传成功，跳转到车主首页
                 mui.toast('上传成功');
                 mui.fire(mycarPage, "pageflowrefresh" );
                 plus.webview.currentWebview().close();
                 mui.redirect('myaccount-mycar', '../myaccount/mycar.html');
             } else {
                 //outLine("上传失败：" + status);
                 wt.close();
                 mui.toast('上传失败');
             }
         }
     );
     task.addData("token", UserInfo.token());
     task.addData("source", source);
     task.start();
 }
 .C#后台代码
  //将base64编码的字符串转为图片并保存
 protected string SaveBase64Image(string source, string path, int userID)
 {
     try
     {
         var now = DateTime.Now;
         string filePath = path + now.ToString("yyyy-MM-dd") + "/" + userID.ToString() + "/";
         string fileName = now.ToString("yyyyMMddhhmmssffff") + ".jpg";
         Log.Debug("filePath:" + filePath + fileName);
         string strbase64 = source.Substring(source.IndexOf(',') + );
         strbase64 = strbase64.Trim('\0');
         //Log.Debug("strbase64:" + strbase64);
         byte[] arr = Convert.FromBase64String(strbase64);
         using (MemoryStream ms = new MemoryStream(arr))
         {
             Log.Debug("进入了MemoryStream");
             Bitmap bmp = new Bitmap(ms);
             if (!Directory.Exists(Server.MapPath(filePath)))
             {
                 Log.Debug("没有Directory");
                 Directory.CreateDirectory(Server.MapPath(filePath));
             }
             //if (!Directory.Exists(filePath))
             //    Log.Debug("没有Directory");
             //Directory.CreateDirectory(filePath);
             //新建第二个bitmap类型的bmp2变量。
             Bitmap bmp2 = new Bitmap(bmp, bmp.Width, bmp.Height);
             //将第一个bmp拷贝到bmp2中
             Graphics draw = Graphics.FromImage(bmp2);
             draw.DrawImage(bmp, , );
             draw.Dispose();
             Log.Debug("保存图片前");
             bmp2.Save(Server.MapPath(filePath + fileName), System.Drawing.Imaging.ImageFormat.Jpeg);
             Log.Debug("保存图片后");
             //bmp.Save("test.bmp", ImageFormat.Bmp);
             //bmp.Save("test.gif", ImageFormat.Gif);
             //bmp.Save("test.png", ImageFormat.Png);
             ms.Close();
             return filePath + fileName;
         }
     }
     catch (Exception ex)
     {
         return null;
     }
 }