Swift上传图片，服务器回应称文件不是'；t图像

正在进行Swift项目，显然我上传的文件不是图像。我也在使用Alamofire实用程序。

let uuid = NSUUID().UUIDString
    print ("MARK -- UUID is " + uuid)
    let image = imageView.image
    Alamofire.upload(.POST, "{RETRACTED}", multipartFormData: {
        multipartFormData in
        if  let imageData = UIImageJPEGRepresentation(image!, 0.6) {
            multipartFormData.appendBodyPart(data: imageData, name: uuid, fileName: uuid + ".png", mimeType: "image/png")
        }
        }, encodingCompletion: {
            encodingResult in
            switch encodingResult {
            case .Success(let upload, _, _):
                upload.responseJSON { response in
                    print(response.request)  // original URL request
                    print(response.response) // URL response
                    print(response.data)     // server data
                    print(response.result)   // result of response serialization
                    if let JSON = response.result.value {
                        print ("JSON '(JSON)")
                        self.displayAlert("Uploaded!", message: "{RETRACTED}", responseButtonText: "{RETRACTED}")
                    }
                }
            case .Failure(let encodingError):
                print(encodingError)
            }
    })

以下是JSON响应（如果需要，我还有PHP服务器端代码）：

JSON{response="该文件不是图像（只接受.png和.jpg/.jpeg图像）。类型为"；responseCode=0；}

谢谢大家。