请问大牛5 plus 中plus.webview.create()用这个接口上传照片到wcf rest指定的接口，后台要怎么写啊！

请问大牛5 plus 中plus.uploader.createUpload（）用这个接口上传照片到wcf rest指定的接口，后台要怎么写啊！
一直不能接收到传过来的值。
我已经能够用这种 方式获取到前面传过来的 stream但不知道怎么解密图片。
public string UploadImg(Stream stream)
{
// HttpRequest request = HttpContext.Current.Request;
//HttpPostedFileBase reqest
if (stream == null)
{
WebOperationContext.Current.OutgoingResponse.StatusCode = HttpStatusCode.NotFound;
return null;
}
StreamReader reader = new StreamReader(stream);
string res = reader.ReadToEnd();
string imgPath = string.Empty;
try
{
long incomingLength = WebOperationContext.Current.IncomingRequest.ContentLength;
WebHeaderCollection w= WebOperationContext.Current.IncomingRequest.Headers;
var s = w["zeng"];
var img = w["base64Img"];

string diskPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "img");
DirectoryInfo di = new DirectoryInfo(diskPath);
if (!di.Exists)
{
di.Create();
}
imgPath = string.Format("{0}\\{1}.{2}", di.FullName, Guid.NewGuid().ToString(), "jpg");

//byte[] arr = Convert.FromBase64String(img.Split(',')[1]);
// MemoryStream ms = new MemoryStream(arr);
var bmp = Bitmap.FromStream(stream);
bmp.Save(imgPath, System.Drawing.Imaging.ImageFormat.Jpeg);
// ms.Close();

}
catch
{
WebOperationContext.Current.OutgoingResponse.StatusCode = HttpStatusCode.NotFound;
}
return imgPath;
}