为什么iPhone不能捕获预览层显示的内容？

Question

我正在尝试创建一个基于AVFoundation框架的拍照应用程序。我有一个预览层在屏幕上，它充满了我想要的整个屏幕。

这是预览层看到的内容：https://ibb.co/47gYQbD

这是我捕获照片后得到的结果：https://ibb.co/qkkbf0N

下面是我创建预览层对象的方法。

let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.videoGravity = .resizeAspectFill
previewLayer.frame = view.bounds
let previewLayerContainer = UIView()
previewLayerContainer.frame = CGRect(x: 0, y: 0, width: view.bounds.size.width, height: view.bounds.size.height)
view.addSubview(previewLayerContainer)
previewLayer.bounds = previewLayerContainer.bounds
previewLayerContainer.layer.addSublayer(previewLayer)

照片设置：

// AVCapturePhotoSettings object
        let photoSettings: AVCapturePhotoSettings
        
        // Capture HEIF photos when supported
        if self.photoOutput.availablePhotoCodecTypes.contains(.hevc) {
            photoSettings = AVCapturePhotoSettings(format:
                [AVVideoCodecKey: AVVideoCodecType.hevc])
        } else {
            photoSettings = AVCapturePhotoSettings()
        }
        
        //Enable auto-flash and high-resolution photos
        if self.captureDeviceInput.device.isFlashAvailable {
            switch currentFlashStatus {
            case .AUTO:
                photoSettings.flashMode = .auto
            case .ON:
                photoSettings.flashMode = .on
            case .OFF:
                photoSettings.flashMode = .off
            }
        }
        
        photoSettings.isHighResolutionPhotoEnabled = true
        
        //Photo Quality Prioritization
        photoOutput.maxPhotoQualityPrioritization = .quality
        photoSettings.photoQualityPrioritization = .quality

Answer 1

捕获的照片和您的屏幕具有不同的纵横比。当您告诉预览层为resizeAspectFill时，它将裁剪摄像机视频源的一部分以填充屏幕。如果要预览整个场景(以在预览中显示黑条为代价)，请改用previewLayer.videoGravity = .resizeAspect。