在 AVCapture Swift 中仅捕获相机预览

Posted 2023-02-23

【中文标题】在 AVCapture Swift 中仅捕获相机预览

【英文标题】：Capture only camerapreview in AVCapture Swift

【发布时间】：2019-01-25 03:18:00

【问题描述】：

这是我的代码

import UIKit
import AVFoundation

class ViewController: UIViewController 

    @IBOutlet weak var cameraView: UIView!

    var image: UIImage!

    var captureSession = AVCaptureSession()
    var backCamera: AVCaptureDevice?
    var frontCamera: AVCaptureDevice?
    var currentCamera: AVCaptureDevice?

    var photoOutput: AVCapturePhotoOutput?

    var cameraPreviewLayer: AVCaptureVideoPreviewLayer?

    override func viewDidLoad() 
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.


    

    override func viewDidAppear(_ animated: Bool) 

        setupCaptureSession()
        setupDevice()
        setupInputOutput()
        setupPreviewLayer()
        startRunningCaptureSession()

    

    @IBAction func cameraButton_Tab(_ sender: Any) 

        let settings = AVCapturePhotoSettings()

//        performSegue(withIdentifier: "showPhoto_Segue", sender: nil)
        photoOutput?.capturePhoto(with: settings, delegate: self)

    

    func setupCaptureSession() 

        captureSession.sessionPreset = AVCaptureSession.Preset.photo

    

    func setupDevice() 

        let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [AVCaptureDevice.DeviceType.builtInWideAngleCamera], mediaType: AVMediaType.video, position: AVCaptureDevice.Position.unspecified)

        let devices = deviceDiscoverySession.devices

        for device in devices 

            if device.position == AVCaptureDevice.Position.back 

                backCamera = device

            else if device.position == AVCaptureDevice.Position.front

                frontCamera = device

            

        

        currentCamera = backCamera

    

    func setupInputOutput() 

        do

            let captureDeviceInput = try AVCaptureDeviceInput(device: currentCamera!)
            captureSession.addInput(captureDeviceInput)
            photoOutput = AVCapturePhotoOutput()
            photoOutput?.setPreparedPhotoSettingsArray([AVCapturePhotoSettings(format: [AVVideoCodecKey : AVVideoCodecType.jpeg])], completionHandler: nil)
            captureSession.addOutput(photoOutput!)

        catch 
            print(error)
        

    

    func setupPreviewLayer() 

        cameraPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        cameraPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
        cameraPreviewLayer?.connection?.videoOrientation = AVCaptureVideoOrientation.portrait
        cameraPreviewLayer!.frame = self.cameraView.bounds
        self.cameraView.layer.insertSublayer(cameraPreviewLayer!, at: 0)

    

    func startRunningCaptureSession() 

        captureSession.startRunning()

    



extension ViewController: AVCapturePhotoCaptureDelegate 

    func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) 
        if let imageData = photo.fileDataRepresentation()
            image = UIImage(data: imageData)

        
    

看图， 我想保存背景颜色为黄色的图像 我可以通过它看到相机

但是我保存图片，好像保存的是整个视图，而不是正方形。

我使 UIImageView 与黄色 UIView 大小相同并保存输出， 它需要整个视图捕获和调整大小。

喜欢用挤压把矩形变成正方形

我怎么不能只捕捉黄色背景大小并保存？

【参考方案1】：

这个didFinishProcessingPhoto 将返回完整的图像，就像相机看到的一样。您不会直接在PreviewLayer 中显示图像。因此，为了获得显示的PreviewLayer 的UIImage，您可以调整捕获图像的大小。

好吧，调整大小也可以通过两种方式完成：一种是保持纵横比，另一种是通过传递确切的大小。我建议使用纵横比，因为它可以确保您的图像不会被任何尺寸挤压或拉伸，而传递错误的尺寸将无法满足您的要求。

调整UIImage 的大小，传递新的CGSize：

extension UIImage 
    func scaleImage(toSize newSize: CGSize) -> UIImage? 
        var newImage: UIImage?
        let newRect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height).integral
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0)
        if let context = UIGraphicsGetCurrentContext(), let cgImage = self.cgImage 
            context.interpolationQuality = .high
            let flipVertical = CGAffineTransform(a: 1, b: 0, c: 0, d: -1, tx: 0, ty: newSize.height)
            context.concatenate(flipVertical)
            context.draw(cgImage, in: newRect)
            if let img = context.makeImage() 
                newImage = UIImage(cgImage: img)
            
            UIGraphicsEndImageContext()
        
        return newImage
    

用法： capturedImage.scaleImage(toSize: CGSize(width: 300, height: 300))

调整UIImage的大小，保持纵横比：

extension UIImage 
    func scaleImage(toWidth newWidth: CGFloat) -> UIImage 
        let scale = newWidth / self.size.width
        let newHeight = self.size.height * scale
        let newSize = CGSize(width: newWidth, height: newHeight)

        let renderer = UIGraphicsImageRenderer(size: newSize)

        let image = renderer.image  (context) in
            self.draw(in: CGRect(origin: CGPoint(x: 0, y: 0), size: newSize))
        
        return image
    

用法： capturedImage.scaleImage(toWidth: 300)

参考：Resize UIImage to 200x200pt/px

更新：

在您的代码中保留以下方法：

@IBAction func cameraButton_Tab(_ sender: Any) 
    let settings = AVCapturePhotoSettings()
    photoOutput?.capturePhoto(with: settings, delegate: self)


extension ViewController: AVCapturePhotoCaptureDelegate 

    func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) 
        if let imageData = photo.fileDataRepresentation()
            let capturedImage = UIImage(data: imageData)
            let cropImage = capturedImage.scaleImage(toWidth: cameraPreviewLayer!.frame.size.width) //It will return the Image size of Camera Preview
        
    

【讨论】：

谢谢，但我有疑问，如果我采用最后一种方法，我在哪里称呼它？什么是 PreviewLayer？

你分配给你的照片

@SohilR.Memon 很抱歉我没有这么快理解。好的，我删除了它，只调用 takeScreenshot，然后调用 UIImageWriteToSavedPhotosAlbum，但它保存黄色方块而不是预览

@PolarisNation 抱歉，请参阅 ***.com/questions/44841331/…，它表示无法进行相机预览截图。您可以使用所述的其他方法