ios - AVCaptureStillImageOutput 和 UIImagePNGRepresentation

Question

我在做一些我认为不应该那么困难的事情上遇到了困难，所以我想我一定是从错误的角度看待问题。为了了解 AVCaptureStillImageOutput 和相机的工作原理，我制作了一个小应用程序。

这个应用程序能够拍摄照片并将其保存为 PNG 文件(我不需要 JPEG)。下次启动应用程序时，它会检查文件是否存在，如果存在，则将文件中存储的图像用作应用程序的背景 View 。这个想法相当简单。

问题是它不起作用。如果有人能告诉我我做错了什么，那将会非常有帮助。

我希望图片以拍摄时在显示屏上的方式显示为背景，但它被旋转或比例错误......等等。

这是相关代码(如果需要，我可以提供更多信息)。

viewDidLoad 方法:

override func viewDidLoad() {
    super.viewDidLoad()

    // For the photo capture:
    captureSession.sessionPreset = AVCaptureSessionPresetHigh

    // Select the appropriate capture devices:
    for device in AVCaptureDevice.devices() {
        // Make sure this particular device supports video.
        if (device.hasMediaType(AVMediaTypeVideo)) {
            // Finally check the position and confirm we've got the back camera.
            if(device.position == AVCaptureDevicePosition.Back) {
                captureDevice = device as? AVCaptureDevice
            }
        }
    }

    tapGesture = UITapGestureRecognizer(target: self, action: Selector("takePhoto"))
    self.view.addGestureRecognizer(tapGesture)

    let filePath = self.toolBox.getDocumentsDirectory().stringByAppendingPathComponent("BackGroundImage@2x.png")

    if !NSFileManager.defaultManager().fileExistsAtPath(filePath) {return}

    let bgImage = UIImage(contentsOfFile: filePath),
    bgView = UIImageView(image: bgImage)
    self.view.addSubview(bgView)
}

处理拍照的方法:

func takePhoto() {
    if !captureSession.running {
        beginPhotoCaptureSession()
        return
    }

    if let videoConnection = stillImageOutput.connectionWithMediaType(AVMediaTypeVideo) {
        stillImageOutput.captureStillImageAsynchronouslyFromConnection(videoConnection) {
            (imageDataSampleBuffer, error) -> Void in
            if error == nil {
                var localImage = UIImage(fromSampleBuffer: imageDataSampleBuffer)
                UIGraphicsBeginImageContext(localImage!.size)
                CGContextRotateCTM (UIGraphicsGetCurrentContext(), CGFloat(M_PI_2))
                //localImage!.drawAtPoint(CGPointZero)
                localImage!.drawAtPoint(CGPoint(x: -localImage!.size.height, y: -localImage!.size.width))
                //localImage!.drawAtPoint(CGPoint(x: -localImage!.size.width, y: -localImage!.size.height))
                localImage = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext()
                localImage = resizeImage(localImage!, toSize: self.view.frame.size)

                if let data = UIImagePNGRepresentation(localImage!) {
                    let bitMapName = "BackGroundImage@2x"
                    let filename = self.toolBox.getDocumentsDirectory().stringByAppendingPathComponent("\(bitMapName).png")
                    data.writeToFile(filename, atomically: true)
                    print("Picture saved: \(bitMapName)\n\(filename)")
                }
            } else {print("Error on taking a picture:\n\(error)")}
        }
    }

    captureSession.stopRunning()
    previewLayer!.removeFromSuperlayer()
}

启动AVCaptureSession的方法:

func beginPhotoCaptureSession() {
    do {let input = try AVCaptureDeviceInput(device: captureDevice)
        captureSession.addInput(input)
    } catch let error as NSError {
        // Handle any errors:
        print(error)
    }

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    previewLayer?.frame = self.view.layer.frame
    self.view.layer.addSublayer(previewLayer!)
    captureSession.startRunning()

    stillImageOutput.outputSettings = [kCVPixelBufferPixelFormatTypeKey:Int(kCVPixelFormatType_32BGRA)]
    if captureSession.canAddOutput(stillImageOutput) {
        captureSession.addOutput(stillImageOutput)
    }
}

以下是使用该应用拍摄的照片的示例:

现在这是我重新启动应用程序时得到的背景:

如果工作正常，两张图片将会相似。

Answer 1

我在屏幕截图中看不到旋转。但是比例是一个问题，当您在 function takePhoto 中绘制它时，它与您的代码有关。你可以试试

func takePhoto() {
    if !captureSession.running {
        beginPhotoCaptureSession()
        return
    }
    if let videoConnection = stillImageOutput.connectionWithMediaType(AVMediaTypeVideo) {
        stillImageOutput.captureStillImageAsynchronouslyFromConnection(videoConnection) {
            (imageDataSampleBuffer, error) -> Void in
            if error == nil {
               if let data = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(imageDataSampleBuffer) {
                    let bitMapName = "BackGroundImage@2x"
                    let filename = self.toolBox.getDocumentsDirectory().stringByAppendingPathComponent("\(bitMapName).png")
                    data.writeToFile(filename, atomically: true)
                    print("Picture saved: \(bitMapName)\n\(filename)")
                }
            } else {print("Error on taking a picture:\n\(error)")}
        }
    }

    captureSession.stopRunning()
    previewLayer!.removeFromSuperlayer()
}