#StackBounty: #ios #swift #avfoundation #zoom #uipangesturerecognizer Pan gesture (hold/drag) zoom on camera like Snapchat

Bounty: 50

I am trying to replicate Snapchat camera’s zoom feature where once you have started recording you can drag your finger up or down and it will zoom in or out accordingly. I have been successful with zooming on pinch but have been stuck on zooming with the PanGestureRecognizer.

Here is the code I’ve tried the problem is that I do not know how to replace the sender.scale that I use for pinch gesture recognizer zooming. I’m using AVFoundation. Basically, I’m asking how I can do the hold zoom (one finger drag) like in TikTok or Snapchat properly.

let minimumZoom: CGFloat = 1.0
let maximumZoom: CGFloat = 15.0
var lastZoomFactor: CGFloat = 1.0
var latestDirection: Int = 0

@objc func panGesture(_ sender: UIPanGestureRecognizer) {

    let velocity = sender.velocity(in: doubleTapSwitchCamButton)
    var currentDirection: Int = 0

    if velocity.y > 0 || velocity.y < 0 {

                let originalCapSession = captureSession
                var devitce : AVCaptureDevice!

                let videoDeviceDiscoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera, .builtInDuoCamera], mediaType: AVMediaType.video, position: .unspecified)
                let devices = videoDeviceDiscoverySession.devices
                devitce = devices.first!

                guard let device = devitce else { return }

                    // Return zoom value between the minimum and maximum zoom values
                    func minMaxZoom(_ factor: CGFloat) -> CGFloat {
                        return min(min(max(factor, minimumZoom), maximumZoom), device.activeFormat.videoMaxZoomFactor)

                        func update(scale factor: CGFloat) {
                            do {

                                try device.lockForConfiguration()
                                defer { device.unlockForConfiguration() }
                                device.videoZoomFactor = factor
                            } catch {

//These 2 lines below are the problematic ones, pinch zoom uses this one below, and the newScaleFactor below that is a testing one that did not work.
                let newScaleFactor = minMaxZoom(sender.scale * lastZoomFactor)
                       //let newScaleFactor = CGFloat(exactly: number + lastZoomFactor)

                    switch sender.state {

                    case .began: fallthrough                
                    case .changed: update(scale: newScaleFactor!)                
                    case .ended:
                        lastZoomFactor = minMaxZoom(newScaleFactor!)
                        update(scale: lastZoomFactor)

                    default: break

        } else {


        latestDirection = currentDirection


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