ios - Swift 中的自定义相机和裁剪图像

Question

我已经创建了一个自定义相机，并实现了下面的代码来裁剪拍摄的图像，我已经在预览层中显示了指南，所以我想裁剪出现在该区域的图像。

func imageByCropToRect(rect:CGRect, scale:Bool) -> UIImage {    
    var rect = rect
    var scaleFactor: CGFloat = 1.0
    if scale  {
        scaleFactor = self.scale
        rect.origin.x *= scaleFactor
        rect.origin.y *= scaleFactor
        rect.size.width *= scaleFactor
        rect.size.height *= scaleFactor
    }

    var image: UIImage? = nil;
    if rect.size.width > 0 && rect.size.height > 0 {
        let imageRef = self.cgImage!.cropping(to: rect)
        image = UIImage(cgImage: imageRef!, scale: scaleFactor, orientation: self.imageOrientation)
    }

    return image!
}

当下面的代码行被注释时给出精确的裁剪图像时，这段代码工作得很好，尽管我希望图像流是全屏的，所以我必须使用下面的代码行。图像有点缩小。

(self.previewLayer as! AVCaptureVideoPreviewLayer).videoGravity = AVLayerVideoGravity.resizeAspectFill

如何解决这个问题？裁剪代码是否错误？

这是完整的类代码

import UIKit
import AVFoundation

class CameraViewController: UIViewController {

    @IBOutlet weak var guideImageView: UIImageView!
    @IBOutlet weak var guidesView: UIView!
    @IBOutlet weak var cameraPreviewView: UIView!
    @IBOutlet weak var cameraButtonView: UIView!

    @IBOutlet weak var captureButton: UIButton!

    var captureSession = AVCaptureSession()
    var previewLayer: CALayer!
    var captureDevice: AVCaptureDevice!

    /// This will be true when the user clicks on the click photo button.
    var takePhoto = false

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        captureSession = AVCaptureSession()
        previewLayer = CALayer()
        takePhoto = false

        requestAuthorization()
    }

    private func userinteractionToButton(_ interaction: Bool) {
        captureButton.isEnabled = interaction
    }

    /// This function will request authorization, If authorized then start the camera.
    private func requestAuthorization() {
        switch AVCaptureDevice.authorizationStatus(for: AVMediaType.video) {
        case .authorized:
            prepareCamera()

        case .denied, .restricted, .notDetermined:
            AVCaptureDevice.requestAccess(for: AVMediaType.video, completionHandler: { (granted) in
                if !Thread.isMainThread {
                    DispatchQueue.main.async {
                        if granted {
                            self.prepareCamera()
                        } else {
                            let alert = UIAlertController(title: "unable_to_access_the_Camera", message: "to_enable_access_go_to_setting_privacy_camera_and_turn_on_camera_access_for_this_app", preferredStyle: UIAlertControllerStyle.alert)
                            alert.addAction(UIAlertAction(title: "ok", style: .default, handler: {_ in
                                self.navigationController?.popToRootViewController(animated: true)
                            }))
                            self.present(alert, animated: true, completion: nil)
                        }
                    }
                } else {
                    if granted {
                        self.prepareCamera()
                    } else {
                        let alert = UIAlertController(title: "unable_to_access_the_Camera", message: "to_enable_access_go_to_setting_privacy_camera_and_turn_on_camera_access_for_this_app", preferredStyle: UIAlertControllerStyle.alert)
                        alert.addAction(UIAlertAction(title: "ok", style: .default, handler: {_ in
                            self.navigationController?.popToRootViewController(animated: true)
                        }))
                        self.present(alert, animated: true, completion: nil)
                    }
                }
            })
        }
    }

    /// Will see if the primary camera is avilable, If found will call method which will asign the available device to the AVCaptureDevice.
    private func prepareCamera() {
        // Resets the session.
        self.captureSession.sessionPreset = AVCaptureSession.Preset.photo

        if #available(iOS 10.0, *) {
            let availableDevices = AVCaptureDevice.DiscoverySession(deviceTypes: [AVCaptureDevice.DeviceType.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .back).devices
            self.assignCamera(availableDevices)
        } else {
            // Fallback on earlier versions
            // development, need to test this on iOS 8
            if let availableDevices = AVCaptureDevice.default(for: AVMediaType.video) {
                self.assignCamera([availableDevices])
            } else {
                self.showAlert()
            }
        }
    }

    /// Assigns AVCaptureDevice to the respected the variable, will begin the session.
    ///
    /// - Parameter availableDevices: [AVCaptureDevice]
    private func assignCamera(_ availableDevices: [AVCaptureDevice]) {
        if availableDevices.first != nil {
            captureDevice = availableDevices.first
            beginSession()
        } else {
            self.showAlert()
        }
    }

    /// Configures the camera settings and begins the session, this function will be responsible for showing the image on the UI.
    private func beginSession() {
        do {
            let captureDeviceInput = try AVCaptureDeviceInput(device: captureDevice)
            captureSession.addInput(captureDeviceInput)
        } catch {
            print(error.localizedDescription)
        }

        let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        self.previewLayer = previewLayer
        self.cameraPreviewView.layer.addSublayer(self.previewLayer)
        self.previewLayer.frame = self.view.layer.frame
        self.previewLayer.frame.origin.y = +self.cameraPreviewView.frame.origin.y
        (self.previewLayer as! AVCaptureVideoPreviewLayer).videoGravity = AVLayerVideoGravity.resizeAspectFill
        self.previewLayer.masksToBounds = true
        self.cameraPreviewView.clipsToBounds = true
        captureSession.startRunning()

        self.view.bringSubview(toFront: self.cameraPreviewView)
        self.view.bringSubview(toFront: self.cameraButtonView)
        self.view.bringSubview(toFront: self.guidesView)

        let dataOutput = AVCaptureVideoDataOutput()
        dataOutput.videoSettings = [((kCVPixelBufferPixelFormatTypeKey as NSString) as String):NSNumber(value:kCVPixelFormatType_32BGRA)]

        dataOutput.alwaysDiscardsLateVideoFrames = true

        if captureSession.canAddOutput(dataOutput) {
            captureSession.addOutput(dataOutput)
        }

        captureSession.commitConfiguration()

        let queue = DispatchQueue(label: "com.letsappit.camera")
        dataOutput.setSampleBufferDelegate(self, queue: queue)

        self.userinteractionToButton(true)
    }


    /// Get the UIImage from the given CMSampleBuffer.
    ///
    /// - Parameter buffer: CMSampleBuffer
    /// - Returns: UIImage?
    func getImageFromSampleBuffer(buffer:CMSampleBuffer, orientation: UIImageOrientation) -> UIImage? {
        if let pixelBuffer = CMSampleBufferGetImageBuffer(buffer) {
            let ciImage = CIImage(cvPixelBuffer: pixelBuffer)
            let context = CIContext()
            let imageRect = CGRect(x: 0, y: 0, width: CVPixelBufferGetWidth(pixelBuffer), height: CVPixelBufferGetHeight(pixelBuffer))

            if let image = context.createCGImage(ciImage, from: imageRect) {
                return UIImage(cgImage: image, scale: UIScreen.main.scale, orientation: orientation)

            }

        }
        return nil
    }

    /// This function will destroy the capture session.
    func stopCaptureSession() {
        self.captureSession.stopRunning()

        if let inputs = captureSession.inputs as? [AVCaptureDeviceInput] {
            for input in inputs {
                self.captureSession.removeInput(input)
            }
        }
    }

    func showAlert() {
        let alert = UIAlertController(title: "Unable to access the camera", message: "It appears that either your device doesn't have camera or its broken", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "cancel", style: .cancel, handler: {_ in
            self.navigationController?.dismiss(animated: true, completion: nil)
        }))
        self.present(alert, animated: true, completion: nil)
    }

    @IBAction func didTapClick(_ sender: Any) {
        userinteractionToButton(false)
        takePhoto = true
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "showImage" {
            let vc = segue.destination as! ShowImageViewController
            vc.image = sender as! UIImage
        }
    }
}

extension CameraViewController: AVCaptureVideoDataOutputSampleBufferDelegate {
    func captureOutput(_ captureOutput: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {

        if connection.isVideoOrientationSupported {
            connection.videoOrientation = .portrait
        }

        if takePhoto {
            takePhoto = false

            // Rotation should be unlocked to work.
            var orientation = UIImageOrientation.up
            switch UIDevice.current.orientation {
            case .landscapeLeft:
                orientation = .left

            case .landscapeRight:
                orientation = .right

            case .portraitUpsideDown:
                orientation = .down

            default:
                orientation = .up
            }

            if let image = self.getImageFromSampleBuffer(buffer: sampleBuffer, orientation: orientation) {
                DispatchQueue.main.async {
                    let newImage = image.imageByCropToRect(rect: self.guideImageView.frame, scale: true)
                    self.stopCaptureSession()
                    self.previewLayer.removeFromSuperlayer()
                    self.performSegue(withIdentifier: "showImage", sender: newImage)
                }
            }
        }
    }
}

这是 View 层次结构图像

Answer 1

目前还不清楚问题出在哪里。我会使用调试器或一些打印语句来确定问题是否出在图像或显示图像的 View 上。打印出裁剪图像的尺寸以确保其正确。

然后，在viewDidAppear中打印出ShowImageViewController中的 ImageView 大小，以确保其正确。