在ios中上传后如何从firebase获取缩略图？

我正在将视频和图像上传到swift中的firebase。现在，当上传完成，然后我得到的图像网址。但url是原始图像。我想当图像或视频上传时，我应该为图像或视频获取Thumnbail图像。我正在使用下面的代码

let imagePath = withName

        let metadata = FIRStorageMetadata()
        metadata.contentType = mimeType
        metadata.customMetadata = ["index": String(describing: index), "contentType": mimeType]

        // Upload file and metadata to the object 'images/mountains.jpg'
        let uploadTask = storageRef.child(imagePath).put(data, metadata: metadata)

        // Listen for state changes, errors, and completion of the upload.
        uploadTask.observe(.resume) { snapshot in
            // Upload resumed, also fires when the upload starts
        }

        uploadTask.observe(.pause) { snapshot in
            // Upload paused
        }

        uploadTask.observe(.progress) { snapshot in
            // Upload reported progress
            let percentComplete =  Double((snapshot.progress?.completedUnitCount)!)/Double(snapshot.progress!.totalUnitCount)
            progress( String(format: "%.2f", percentComplete))
            print(percentComplete)
        }

        uploadTask.observe(.success) { snapshot in
            // Upload completed successfully
            //Download the the image from url and save it as Data in local directory
            print(snapshot.metadata?.downloadURL()?.absoluteString ?? "no url found......")
            completion(.success, (snapshot.metadata?.downloadURL()?.absoluteString), DIError.noResponse)

            // self.startDownloading(downloadUrl: (snapshot.metadata?.downloadURL()?.absoluteString)!, imageName: imagePath)
        }

---

我们举了一个如何使用云存储的云函数生成缩略图的示例：

---

缩略图会保存回云存储，然后您可以下载大小合适的照片。

FIRStorage仅用于存储数据。它不会自动创建缩略图。您需要使用Firebase函数并添加生成缩略图的代码。这仅适用于图像。我应该使用什么来获取视频文件的缩略图？