AVCaptureSessionPreset:如果最大预设为 1088x1920,为什么标准 iPhone 相机保存 2448 × 3264?

AVCaptureSessionPreset: why does standard iPhone camera save 2448 × 3264, if max preset is 1088x1920?

我正在编写使用相机的小型 iOS 应用程序。我使用 AVFoundation 框架 API,并考虑 AVCaptureSessionPreset 的最大质量。在我的具体设备上是:
CaptureQualityPhoto = (640 852)
CaptureQualityHigh = (1088 1920)
CaptureQualityMedium = (368 480)
CaptureQuality1280x720 = (720 1280)
CaptureQuality640x480 = (480 640)
CaptureQualityiFrame960x540 = (540 960)

标准相机应用程序保存分辨率为 2448 × 3264 的照片。
假设我想以相同的分辨率保存照片,但我能达到的最高质量是 1088 x 1920
当然,我可以调整大小 UIImage,但这是最好的方法吗?
标准应用程序是否可以访问更高分辨率或仅使用一些缩放和插值?

编辑: 现在我使用 2248x3264 照片预设的工作代码如下所示:

-(void) initCapturingDevice
{
    [self releaseCapturingDevice];

    self.capture_session = [[AVCaptureSession alloc] init];
    [self.capture_session beginConfiguration];

    self.video_data_output = [[AVCaptureVideoDataOutput alloc] init];
    self.video_data_output.videoSettings = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
    [self.video_data_output setSampleBufferDelegate:self queue:dispatch_get_main_queue()];
    [self.capture_session addOutput:self.video_data_output];

    self.capture_session.sessionPreset = AVCaptureSessionPresetPhoto; 
    // some code here ...  
}

您可以获得最高质量的照片(在我的 phone 上是 4032 x 3024)AVCaptureSessionPresetPhotoAVCaptureStillImageOutput:

let captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
let input = try! AVCaptureDeviceInput(device: captureDevice)

captureSession.addInput(input)
captureSession.sessionPreset = AVCaptureSessionPresetPhoto

let stillImageOutput = AVCaptureStillImageOutput()
captureSession.addOutput(stillImageOutput)

captureSession.startRunning()

let connection = stillImageOutput.connectionWithMediaType(AVMediaTypeVideo)
stillImageOutput.captureStillImageAsynchronouslyFromConnection(connection) { (sampleBuffer, error) in
    print("maximum quality photo: \(sampleBuffer)\n")
}