斯威夫特:同时自动对焦/曝光和连续自动聚焦/曝光？

Question

现在，在我的相机应用程序中，我让用户触碰任何地方来设置焦点和曝光，但我如何才能像苹果的相机应用程序那样，在这两个世界中发挥最好的效果呢？

例如，用户可能希望将注意力集中在前景上，但如果场景发生了足够大的变化，则应该返回到continuousAutoFocus。同样，如果用户将相机指向光线，它应该改变曝光以使它看起来正确，然后当相机回到场景时，它应该再次修复曝光，这样就不会太暗了。然而，他们仍然可以选择让它变得更轻或更暗，这取决于他们通过相机的视角接触到的东西。

现在，当视图出现时，我将默认设置为屏幕中心：

func setDefaultFocusAndExposure() {

    let focusPoint = CGPoint(x:0.5,y:0.5)

    if let device = AVCaptureDevice.default(for:AVMediaType.video) {
        do {
            try device.lockForConfiguration()
            if device.isFocusPointOfInterestSupported {
                print(focusPoint)
                device.focusPointOfInterest = focusPoint
                device.focusMode = AVCaptureDevice.FocusMode.autoFocus
            }
            if device.isExposurePointOfInterestSupported {
                device.exposurePointOfInterest = focusPoint
                device.exposureMode = AVCaptureDevice.ExposureMode.autoExpose
            }
            device.unlockForConfiguration()

        } catch {
            // Handle errors here
            print("There was an error focusing the device's camera")
        }
    }

}

此外，我还让用户根据接触的位置设置焦点和曝光：

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    let bounds = UIScreen.main.bounds

    let touchPoint = touches.first! as UITouch
    let screenSize = bounds.size
    let focusPoint = CGPoint(x: touchPoint.location(in: view).y / screenSize.height, y: 1.0 - touchPoint.location(in: view).x / screenSize.width)

    if let device = AVCaptureDevice.default(for:AVMediaType.video) {
        do {
            try device.lockForConfiguration()
            if device.isFocusPointOfInterestSupported {
                device.focusPointOfInterest = focusPoint
                device.focusMode = AVCaptureDevice.FocusMode.autoFocus
            }
            if device.isExposurePointOfInterestSupported {
                device.exposurePointOfInterest = focusPoint
                device.exposureMode = AVCaptureDevice.ExposureMode.autoExpose
            }
            device.unlockForConfiguration()

        } catch {
            // Handle errors here
            print("There was an error focusing the device's camera")
        }
    }
}

Answer 1

弄明白了。首先，我在myViewDidAppear上调用一个设置默认焦点和曝光模式的方法：

@objc func setDefaultFocusAndExposure() {

    if let device = AVCaptureDevice.default(for:AVMediaType.video) {
        do {
            try device.lockForConfiguration()
                device.isSubjectAreaChangeMonitoringEnabled = true
                device.focusMode = AVCaptureDevice.FocusMode.continuousAutoFocus
                device.exposureMode = AVCaptureDevice.ExposureMode.continuousAutoExposure
            device.unlockForConfiguration()

        } catch {
            // Handle errors here
            print("There was an error focusing the device's camera")
        }
    }
}

这里的诀窍不是把autoFocus和continuousAutoFocus混为一谈。这样，在默认情况下，它会不断地观察场景，并设置焦点和曝光。同时，isSubjectAreaChangeMonitorEnabled也是一个非常重要的部分。这样，当场景改变焦点或曝光时，您可以注册一个通知来调用一个函数，这样您就可以切换焦点模式。很快会有更多的报道。

在触摸屏幕时，可以根据某一点设置焦点和曝光：

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    let bounds = UIScreen.main.bounds

    let touchPoint = touches.first! as UITouch
    let screenSize = bounds.size
    let focusPoint = CGPoint(x: touchPoint.location(in: view).y / screenSize.height, y: 1.0 - touchPoint.location(in: view).x / screenSize.width)

    if let device = AVCaptureDevice.default(for:AVMediaType.video) {
        do {
            try device.lockForConfiguration()
            if device.isFocusPointOfInterestSupported {
                device.focusPointOfInterest = focusPoint
                device.focusMode = AVCaptureDevice.FocusMode.autoFocus
            }
            if device.isExposurePointOfInterestSupported {
                device.exposurePointOfInterest = focusPoint
                device.exposureMode = AVCaptureDevice.ExposureMode.autoExpose
            }
            device.unlockForConfiguration()

        } catch {
            // Handle errors here
            print("There was an error focusing the device's camera")
        }
    }
}

在viewDidLoad中注册通知，以便将焦点和曝光模式设置为连续模式。在这里，我只是调用了一个函数，该函数设置了calling的默认设置：

    NotificationCenter.default.addObserver(self,
                                           selector: #selector(self.setDefaultFocusAndExposure),
                                           name: NSNotification.Name.AVCaptureDeviceSubjectAreaDidChange,
                                           object: nil)

不要忘记删除NotificationCenter中的观察者：

deinit {
    NotificationCenter.default.removeObserver(self)
}