从视频拍摄快照之前如何传递width和height参数

Question

我正在从视频中拍摄快照，它工作正常，但是我想要的是在拍摄快照之前，我想通过自定义宽度和高度，以便获得不同的图像尺寸而不是原始尺寸。

  func loadVideoWithVideoURL(_ videoURL: URL) {
           print("load video url \(videoURL)")
        let asset = AVURLAsset(url: videoURL)
        let generator = AVAssetImageGenerator(asset: asset)
        generator.appliesPreferredTrackTransform = true
        let time = NSValue(time: CMTimeMakeWithSeconds(CMTimeGetSeconds(asset.duration)/2, preferredTimescale: asset.duration.timescale))
        generator.generateCGImagesAsynchronously(forTimes: [time]) { [weak self] _, image, _, _, _ in
        if let image = image, let data = UIImage(cgImage: image).pngData() {

       let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
       let uniqueImageName = videoURL.deletingPathExtension().lastPathComponent
         print("/\(uniqueImageName).JPG")
        let imageURL = urls[0].appendingPathComponent("\(uniqueImageName).jpg")
        let videoURL1 = urls[0].appendingPathComponent("\(uniqueImageName).mov")

//writing data here
       try? data.write(to: imageURL, options: [.atomic])
         }
    }

有什么建议吗？

预先感谢！