CODEWITHSUNDEEP
iosautofocusavcapturedeviceavcapture
Kartick Vaddadi
Kartick Vaddadi

Reputation: 4998

How do I undo tap to focus / meter?

In my camera app, I'm thinking of supporting tap to focus and meter. I have found, as a user, that my finger sometimes accidentally touches the screen somewhere, and it focuses there, so I want to undo it. In my app, I'm thinking of adding a Reset Focus button, which would undo the tap to focus: it would tell iOS to focus whereever it thinks is best (as it was before the tap to focus).

Does iOS offer an API for this?

When the user taps at a point, I can assign to focusPointOfInterest and exposurePointOfInterest in AVCaptureDevice. But I don't see functions clearFocusPointOfInterest() and clearExposurePointOfInterest(). How do I do this?

Upvotes: 1

Views: 255

Answers (1)

Melissa
Melissa

Reputation: 178

You need to set the focus to .continousAutoFocus, the exposure to .continuousAutoExposure, and the focal point to CGPoint(x:0.5,y:0.5). The following focus and autofocus code works for me.

    @IBAction private func doFocusAndExpose(_ gestureRecognizer: UITapGestureRecognizer) {
        let devicePoint = previewView.videoPreviewLayer.captureDevicePointConverted(fromLayerPoint: gestureRecognizer.location(in: gestureRecognizer.view))
        focus(with: .autoFocus, exposureMode: .autoExpose, at: devicePoint)
    }

    @IBAction private func doAutofocus(_ gestureRecognizer: UITapGestureRecognizer) {
        let devicePoint = CGPoint(x:0.5,y:0.5)
        focus(with: .continuousAutoFocus, exposureMode: .continuousAutoExposure, at: devicePoint)
    }

    private func focus(with focusMode: AVCaptureDevice.FocusMode,
                       exposureMode: AVCaptureDevice.ExposureMode,
                       at devicePoint: CGPoint) {

        sessionQueue.async {
            let device = self.videoDeviceInput.device
            do {
                try device.lockForConfiguration()

                if device.isFocusPointOfInterestSupported && device.isFocusModeSupported(focusMode) {
                    device.focusPointOfInterest = devicePoint
                    device.focusMode = focusMode
                }

                if device.isExposurePointOfInterestSupported && device.isExposureModeSupported(exposureMode) {
                    device.exposurePointOfInterest = devicePoint
                    device.exposureMode = exposureMode
                }

                device.unlockForConfiguration()
            } catch {
                print("Could not lock device for configuration: \(error)")
            }
        }
    }

Upvotes: 0

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