iOS 点击对焦答案

【问题标题】：iOS tap to focusiOS 点击对焦
【发布时间】：2015-01-22 10:11:35
【问题描述】：

我使用此代码在 iOS 自定义相机应用程序中实现 Tap-to-Focus，但它不起作用。这是代码

override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
    let touchPer = touches.anyObject() as UITouch
    let screenSize = UIScreen.mainScreen().bounds.size
    var focus_x = touchPer.locationInView(self.view).x / screenSize.width
    var focus_y = touchPer.locationInView(self.view).y / screenSize.height

    if let device = captureDevice {
        if(device.lockForConfiguration(nil)) {
            device.focusMode = AVCaptureFocusMode.ContinuousAutoFocus

            device.focusPointOfInterest = CGPointMake(focus_x, focus_y)
            device.exposureMode = AVCaptureExposureMode.ContinuousAutoExposure
            device.unlockForConfiguration()
        }
    }
}

【问题讨论】：

它不起作用怎么办？会产生什么错误？预期的行为是什么？实际行为是什么？
我触摸一点。并且重点应该在这一点上。但没有效果。它没有集中在那个点上。相反，它始终处于无限远焦点。那就是问题所在。 @大卫
你有没有通过它来确保两个 if 都被采纳？
是的。我在每个 if 后面放了一个 println()。他们正在经历 ifs。
为什么我的问题被否决了？

标签： ios swift avcapturesession

【解决方案1】：

videoView: UIView 显示视频，cameraDevice: AVCaptureDevice，以下似乎对我有用：

override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
    var touchPoint = touches.first as! UITouch
    var screenSize = videoView.bounds.size
    var focusPoint = CGPoint(x: touchPoint.locationInView(videoView).y / screenSize.height, y: 1.0 - touchPoint.locationInView(videoView.x / screenSize.width)

    if let device = cameraDevice {
        if(device.lockForConfiguration(nil)) {
            if device.focusPointOfInterestSupported {
                device.focusPointOfInterest = focusPoint
                device.focusMode = AVCaptureFocusMode.AutoFocus
            }
            if device.exposurePointOfInterestSupported {
                device.exposurePointOfInterest = focusPoint
                device.exposureMode = AVCaptureExposureMode.AutoExpose
            }
            device.unlockForConfiguration()
        }
    }
}

请注意，我必须交换 x 和 y 坐标，并将 x 坐标从 1 重新映射到 0，而不是从 0 到 1 — ~~不知道为什么会这样，但似乎有必要让它正常工作（尽管测试它也有点棘手）~~。

编辑：Apple's documentation 解释了坐标变换的原因。

此外，设备可能支持兴趣焦点。您使用 focusPointOfInterestSupported 测试支持。如果支持，您可以使用 focusPointOfInterest 设置焦点。您传递一个 CGPoint，其中 {0,0} 代表图片区域的左上角，{1,1} 代表横向模式下的右下角，主页按钮在右侧——即使设备处于纵向模式也适用.

在我的示例中，我一直使用.ContinuousAutoFocus 和.ContinuousAutoExposure，但文档表明.AutoFocus 是正确的选择。奇怪的是文档没有提到.AutoExpose，但我在我的代码中使用它并且它工作正常。

我还修改了我的示例代码以包含 .focusPointOfInterestSupported 和 .exposurePointOfInterestSupported 测试 — 文档还提到使用给定焦点/曝光模式的 isFocusModeSupported: 和 isExposureModeSupported: 方法来测试它是否适用于给定设备，但我假设如果设备支持兴趣点模式，那么它也支持自动模式。在我的应用中似乎一切正常。

【讨论】：

device.focusMode = AVCptureFocusMode.ContinuousAutoExposure 是错误的。应该是“ContinuousAutoFocus”
更简单的是，如果您使用的是 AVCaptureVideoPreviewLayer 类，则可以使用 captureDevicePointOfInterestForPoint
请参阅我的答案以获得该答案的 Swift 3 版本。

【解决方案2】：

Swift 3.0 解决方案

使用 Swift 3 将 Cody 的答案转换为可行的解决方案。

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    let touchPoint = touches.first! as UITouch
    let screenSize = cameraView.bounds.size
    let focusPoint = CGPoint(x: touchPoint.location(in: cameraView).y / screenSize.height, y: 1.0 - touchPoint.location(in: cameraView).x / screenSize.width)

    if let device = captureDevice {
        do {
            try device.lockForConfiguration()
            if device.isFocusPointOfInterestSupported {
                device.focusPointOfInterest = focusPoint
                device.focusMode = AVCaptureFocusMode.autoFocus
            }
            if device.isExposurePointOfInterestSupported {
                device.exposurePointOfInterest = focusPoint
                device.exposureMode = AVCaptureExposureMode.autoExpose
            }
            device.unlockForConfiguration()

        } catch {
            // Handle errors here
        }
    }
}

【讨论】：

【解决方案3】：

 device.focusPointOfInterest = focusPoint
 device.focusMode = AVCaptureFocusMode.AutoFocus
 device.exposurePointOfInterest = focusPoint
 device.exposureMode = AVCaptureExposureMode.ContinuousAutoExposure

我不知道为什么会这样，但确实如此。

【讨论】：

【解决方案4】：

你应该在focusPointOfInterest 上阅读Apple docs，它说了三件重要的事情：

为此属性设置值不会启动聚焦操作。要将相机聚焦在兴趣点上，首先设置此属性的值，然后将 focusMode 属性设置为 autoFocus 或 ContinuousAutoFocus。

此属性的 CGPoint 值使用坐标系，其中 {0,0} 是图片区域的左上角，{1,1} 是右下角。无论实际设备方向如何，此坐标系始终相对于具有右侧主页按钮的横向设备方向。您可以使用 AVCaptureVideoPreviewLayer 方法在此坐标系和视图坐标之间进行转换。

在更改此属性的值之前，您必须调用 lockForConfiguration() 以获取对设备配置属性的独占访问权限。否则，设置此属性的值会引发异常。完成设备配置后，调用 unlockForConfiguration() 以释放锁定并允许其他设备配置设置。

这是一个实现所有这些的实现：

// In your camera preview view    
@objc private func cameraViewTapped(with gestureRecognizer: UITapGestureRecognizer) {
    let location = gestureRecognizer.location(in: self)
    addFocusIndicatorView(at: location) // If you want to indicate it in the UI

    // This is the point you want to pass to your capture device
    let captureDeviceLocation = previewLayer.captureDevicePointConverted(fromLayerPoint: location)

    // Somehow pass the point to where your AVCaptureDevice is
    viewDelegate?.cameraPreviewView(self, didTapToFocusAt: captureDeviceLocation) 
}


// In your camera controller
func focus(at point: CGPoint) {
    guard let device = videoDevice else {
        return
    }

    guard device.isFocusPointOfInterestSupported, device.isExposurePointOfInterestSupported else {
        return
    }

    do {
        try device.lockForConfiguration()

        device.focusPointOfInterest = point
        device.exposurePointOfInterest = point

        device.focusMode = .continuousAutoFocus
        device.exposureMode = .continuousAutoExposure

        device.unlockForConfiguration()
    } catch {
        print(error)
    }
}

【讨论】：

这与之前的其他答案有何不同？
@AshleyMills 接受的答案没有提到AVCaptureVideoPreviewLayer.captureDevicePointConverted(fromLayerPoint:) - 甚至以笨拙的手动方式这样做。这是 Swift 4，公认的答案在 Swift 2 中。此外，这个答案有来源，并遵循 Swift 风格约定/最佳实践。我不明白你为什么认为这会引起反对。

【解决方案5】：

设置兴趣点的更好方法：

首先计算兴趣点：

 let devicePoint: CGPoint = (self.previewView.layer as!  AVCaptureVideoPreviewLayer).captureDevicePointOfInterestForPoint(gestureRecognizer.locationInView(gestureRecognizer.view))

然后设置关注点：

let device: AVCaptureDevice! = self.videoDeviceInput!.device

    do {
        try device.lockForConfiguration()

        if device.focusPointOfInterestSupported && device.isFocusModeSupported(focusMode){

            device.focusPointOfInterest = devicePoint
            device.focusMode = focusMode
        }

        device.unlockForConfiguration()

    }catch{
        print(error)
    }

【讨论】：

【解决方案6】：

你必须以正确的顺序调用方法：

if(device.lockForConfiguration(nil)) {

    device.focusPointOfInterest = CGPointMake(focus_x, focus_y)
    device.focusMode = AVCaptureFocusMode.ContinuousAutoFocus

    device.exposureMode = AVCaptureExposureMode.ContinuousAutoExposure
    device.unlockForConfiguration()
}

在设置焦点模式之前设置兴趣点，否则焦点将放在上一个兴趣点上。

同样适用于exposurePointOfInterest。

【讨论】：

【解决方案7】：

Swift 5.0 版本

// The back camera as default device
var captureDevice: AVCaptureDevice? {
    return AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back)
}

// The camera view.
var cameraView: UIView!

// The layer that contains the camera output
var previewLayer: AVCaptureVideoPreviewLayer

// The focus square view - the yellow one ;)
var squareFocusView: UIView

// User taps on screen to select focus
@IBAction func tapToFocus(_ sender: UITapGestureRecognizer) {
    // make sure we capture one tap only
    if (sender.state == .ended) {
        
        guard let captureDevice = captureDevice else {
            return
        }
        
        let tappedFocusPoint = sender.location(in: cameraView)
        
        // we need to move the focus point to be the center of the tap instead of (0.0, 0.0)
        let centerX = tappedFocusPoint.x - (squareFocusView.frame.size.width / 2.0)
        let centerY = tappedFocusPoint.y - (squareFocusView.frame.size.height / 2.0)

        let focusPoint = CGPoint(x: centerX, y: centerY)
        
        // we need to remap the point because of different coordination systems.
        let convertedFocusPoint = previewLayer.captureDevicePointConverted(fromLayerPoint: focusPoint)
        
        do {
            // changing focusMode and exposureMode requires the device config to be locked.
            try captureDevice.lockForConfiguration()
            
            if (captureDevice.isFocusModeSupported(.autoFocus) && captureDevice.isFocusPointOfInterestSupported) {
                captureDevice.focusPointOfInterest = convertedFocusPoint
                captureDevice.focusMode = .autoFocus
            }
            
            if (captureDevice.isExposureModeSupported(.autoExpose) && captureDevice.isExposurePointOfInterestSupported) {
                captureDevice.exposurePointOfInterest = convertedFocusPoint
                captureDevice.exposureMode = .autoExpose
            }
            
            // unlocks device config
            captureDevice.unlockForConfiguration()
            
        } catch {
            // handle error here
        }
    }
}

【讨论】：