在swift 5中从UIImage中删除白色背景

Posted 2023-03-16

【中文标题】在swift 5中从UIImage中删除白色背景

【英文标题】：Delete white background from UIImage in swift 5

【发布时间】：2020-11-09 16:45:46

【问题描述】：

我正在尝试保存从相机拍摄的照片的 2 个副本，一个是照片本身，另一个是照片 + 表情符号隐藏出现在那里的人脸。

现在我只得到原始照片+白色背景和表情符号面孔的图像，而不是背后的照片。

这是我用来将表情符号放在脸上的代码：

private func detectFace(in image: CVPixelBuffer) 
        let faceDetectionRequest = VNDetectFaceLandmarksRequest(completionHandler:  (request: VNRequest, error: Error?) in
            DispatchQueue.main.async 
                if let results = request.results as? [VNFaceObservation] 
                    self.handleFaceDetectionResults(results)
                 else 
                    self.clearDrawings()
                
            
        )
        let imageRequestHandler = VNImageRequestHandler(cvPixelBuffer: image, orientation: .leftMirrored, options: [:])
        try? imageRequestHandler.perform([faceDetectionRequest])
    
    
    private func handleFaceDetectionResults(_ observedFaces: [VNFaceObservation]) 
        
        self.clearDrawings()
        
        let facesBoundingBoxes: [CAShapeLayer] = observedFaces.flatMap( (observedFace: VNFaceObservation) -> [CAShapeLayer] in
            let faceBoundingBoxOnScreen = self.previewLayer.layerRectConverted(fromMetadataOutputRect: observedFace.boundingBox)
            
            let image = UIImage(named: "happy_emoji.png")
            let imageView = UIImageView(image: image!)
            imageView.frame = faceBoundingBoxOnScreen
            showCamera.addSubview(imageView)
            let newDrawings = [CAShapeLayer]()
            
            return newDrawings
        )
        
        self.drawings = facesBoundingBoxes
    
    
    private func clearDrawings() 
        showCamera.subviews.forEach( $0.removeFromSuperview() )
    

这是我用来保存图像的代码：

@IBAction func onPhotoTaken(_ sender: Any) 
        
        let settings = AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.hevc])
        self.photoOutput.capturePhoto(with: settings, delegate: self)
        
        
        UIGraphicsBeginImageContextWithOptions(showCamera.frame.size, false, 0.0)
        if let context = UIGraphicsGetCurrentContext() 
            showCamera.layer.render(in: context)
        
        let outputImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        
        let topImage = outputImage
        let bottomImage = imageReciber

        let size = CGSize(width: topImage!.size.width, height: topImage!.size.height + bottomImage.size.height)
        UIGraphicsBeginImageContextWithOptions(size, false, 0.0)

        topImage!.draw(in: CGRect(x: 0, y: 0, width: size.width, height: topImage!.size.height))
        bottomImage.draw(in: CGRect(x: 0, y: topImage!.size.height, width: size.width, height: bottomImage.size.height))

        let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        
        
        UIImageWriteToSavedPhotosAlbum(newImage, nil, nil, nil)
    
    
    func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) 
        
        guard let imageData = photo.fileDataRepresentation()
            else  return 
        
        let image = UIImage(data: imageData)
        
        showCamera.image = image
        imageReciber = image!
        UIImageWriteToSavedPhotosAlbum(showCamera.image!, nil, nil, nil)
    

我尝试了不同的解决方案来删除白色背景（或黑色，取决于我是否在“渲染”部分设置了 false 或 true。但我总是得到白色背景的表情符号图像。

请帮我获取没有白色/黑色背景和拍摄照片的表情符号图像。

我的完整代码是：

import UIKit
import AVFoundation
import Vision


class cameraViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate, AVCapturePhotoCaptureDelegate 
    
    private let captureSession = AVCaptureSession()
    private lazy var previewLayer = AVCaptureVideoPreviewLayer(session: self.captureSession)
    private let videoDataOutput = AVCaptureVideoDataOutput()
    private var drawings: [CAShapeLayer] = []
    private let photoOutput = AVCapturePhotoOutput()
    
    var imageReciber = UIImage()
    
    @IBOutlet weak var showCamera: UIImageView!
    
    override func viewDidLoad() 
        super.viewDidLoad()
        self.addCameraInput()
        self.showCameraFeed()
        self.getCameraFrames()
        self.captureSession.startRunning()
    
    
    override func viewDidLayoutSubviews() 
        super.viewDidLayoutSubviews()
        self.previewLayer.frame = self.showCamera.frame
    
    
    func captureOutput(
        _ output: AVCaptureOutput,
        didOutput sampleBuffer: CMSampleBuffer,
        from connection: AVCaptureConnection) 
        
        guard let frame = CMSampleBufferGetImageBuffer(sampleBuffer) else 
            debugPrint("unable to get image from sample buffer")
            return
        
        self.detectFace(in: frame)
    
    
    private func addCameraInput() 
        guard let device = AVCaptureDevice.DiscoverySession(
            deviceTypes: [.builtInWideAngleCamera, .builtInDualCamera, .builtInTrueDepthCamera],
            mediaType: .video,
            position: .back).devices.first else 
                fatalError("No back camera device found, please make sure to run SimpleLaneDetection in an ios device and not a simulator")
        
        let cameraInput = try! AVCaptureDeviceInput(device: device)
        self.captureSession.addInput(cameraInput)
        captureSession.addOutput(photoOutput)
    
    
    private func showCameraFeed() 
        self.previewLayer.videoGravity = .resizeAspectFill
        self.showCamera.layer.addSublayer(self.previewLayer)
        self.previewLayer.frame = self.showCamera.frame
    
    
    private func getCameraFrames() 
        self.videoDataOutput.videoSettings = [(kCVPixelBufferPixelFormatTypeKey as NSString) : NSNumber(value: kCVPixelFormatType_32BGRA)] as [String : Any]
        self.videoDataOutput.alwaysDiscardsLateVideoFrames = true
        self.videoDataOutput.setSampleBufferDelegate(self, queue: DispatchQueue(label: "camera_frame_processing_queue"))
        self.captureSession.addOutput(self.videoDataOutput)
        guard let connection = self.videoDataOutput.connection(with: AVMediaType.video),
            connection.isVideoOrientationSupported else  return 
        connection.videoOrientation = .portrait
    
    
    private func detectFace(in image: CVPixelBuffer) 
        let faceDetectionRequest = VNDetectFaceLandmarksRequest(completionHandler:  (request: VNRequest, error: Error?) in
            DispatchQueue.main.async 
                if let results = request.results as? [VNFaceObservation] 
                    self.handleFaceDetectionResults(results)
                 else 
                    self.clearDrawings()
                
            
        )
        let imageRequestHandler = VNImageRequestHandler(cvPixelBuffer: image, orientation: .leftMirrored, options: [:])
        try? imageRequestHandler.perform([faceDetectionRequest])
    
    
    private func handleFaceDetectionResults(_ observedFaces: [VNFaceObservation]) 
        
        self.clearDrawings()
        
        let facesBoundingBoxes: [CAShapeLayer] = observedFaces.flatMap( (observedFace: VNFaceObservation) -> [CAShapeLayer] in
            let faceBoundingBoxOnScreen = self.previewLayer.layerRectConverted(fromMetadataOutputRect: observedFace.boundingBox)
            
            let image = UIImage(named: "happy_emoji.png")
            let imageView = UIImageView(image: image!)
            imageView.frame = faceBoundingBoxOnScreen
            showCamera.addSubview(imageView)
            let newDrawings = [CAShapeLayer]()
            
            return newDrawings
        )
        
        self.drawings = facesBoundingBoxes
    
    
    private func clearDrawings() 
        showCamera.subviews.forEach( $0.removeFromSuperview() )
    
    
    
    @IBAction func onPhotoTaken(_ sender: Any) 
        
        let settings = AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.hevc])
        self.photoOutput.capturePhoto(with: settings, delegate: self)
        
        
        UIGraphicsBeginImageContextWithOptions(showCamera.frame.size, false, 0.0)
        if let context = UIGraphicsGetCurrentContext() 
            showCamera.layer.render(in: context)
        
        let outputImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        
        let topImage = outputImage
        let bottomImage = imageReciber

        let size = CGSize(width: topImage!.size.width, height: topImage!.size.height + bottomImage.size.height)
        UIGraphicsBeginImageContextWithOptions(size, false, 0.0)

        topImage!.draw(in: CGRect(x: 0, y: 0, width: size.width, height: topImage!.size.height))
        bottomImage.draw(in: CGRect(x: 0, y: topImage!.size.height, width: size.width, height: bottomImage.size.height))

        let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        
        
        UIImageWriteToSavedPhotosAlbum(newImage, nil, nil, nil)
    
    
    func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) 
        
        guard let imageData = photo.fileDataRepresentation()
            else  return 
        
        let image = UIImage(data: imageData)
        
        //Se añade la imagen capturada desde el Buffer a imageView y se le da un borde algo redondeado para que quede bien.
        showCamera.image = image
        imageReciber = image!
        UIImageWriteToSavedPhotosAlbum(showCamera.image!, nil, nil, nil)
    
   
    

提前谢谢你。

【参考方案1】：

在更冷静地研究问题后，我发现了如何解决我的问题。

问题是我试图在从视频流中获取图像之前将图像打印到文件中，为了解决这个问题，我创建了一个在拍摄图像后执行的新函数，现在一切正常。

    func saveEmoji() 
        showCamera.backgroundColor = UIColor.clear
        UIGraphicsBeginImageContextWithOptions(showCamera.frame.size, true, 0.0)
        if let context = UIGraphicsGetCurrentContext() 
            showCamera.layer.render(in: context)
        
        let outputImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        var topImage = outputImage
        
        UIImageWriteToSavedPhotosAlbum(topImage!, nil, nil, nil)
        topImage = nil
    

保存第一张图片后调用该函数：

    func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) 
        
        guard let imageData = photo.fileDataRepresentation()
            else  return 
        
        let image = UIImage(data: imageData)
        
        showCamera.image = image
        imageReciber = image!
        UIImageWriteToSavedPhotosAlbum(showCamera.image!, nil, nil, nil)
        saveEmoji()