Pinch to zoom out using UIPinchGestureRecognizer

Question

Strangely, my app's UIPinchGestureRecognizer is making it so that moving my fingers together zooms in, and moving my fingers apart zooms out -- which is the opposite of how iOS normally works.

I don't think it's relevant, but: I'm using this in a SpriteKit application.

What am I doing wrong? How do I make UIPinchGestureRecognizer enable the normal iOS pinch-out-to-zoom-in and pinch-in-to-zoom-out behavior?

let pinch = UIPinchGestureRecognizer(target: self, action: #selector(GameScene.pinchZoom))

self.thisView?.addGestureRecognizer(pinch)

var normalCameraScale: CGFloat?
var accumulatedCameraScale: CGFloat = 1.0
    
@objc func pinchZoom(_ gesture: UIPinchGestureRecognizer) {
    if self.normalCameraScale == nil {
        self.normalCameraScale = self.camera?.xScale ?? 1.0
        self.accumulatedCameraScale = self.normalCameraScale!
    }
    
    let maxScale: CGFloat = 10.0
        
    
    let newScale = gesture.scale * self.accumulatedCameraScale
        
    if newScale <= maxScale && newScale >= self.normalCameraScale! {
        self.camera?.setScale(newScale)
    }
        
    if gesture.state == .ended {
        self.accumulatedCameraScale = self.camera?.xScale ?? 1.0
    }
        
        
}

Thanks

Answer 1

As described here, this formula solves this problem:

self.accumulatedCameraScale * 1 / gesture.scale

The full function:

var normalCameraScale: CGFloat?
var accumulatedCameraScale: CGFloat = 1.0
    
@objc func pinchZoom(_ gesture: UIPinchGestureRecognizer) {
  if self.normalCameraScale == nil {
       self.normalCameraScale = self.camera?.xScale ?? 1.0
       self.accumulatedCameraScale = self.normalCameraScale!
  }
    
  let maxScale: CGFloat = 10.0
        
  //This formula makes it work correctly:
  let newScale = self.accumulatedCameraScale * 1 / gesture.scale
        
  if newScale <= maxScale && newScale >= self.normalCameraScale! {
     self.camera?.setScale(newScale)
  }
        
  if gesture.state == .ended {
     self.accumulatedCameraScale = self.camera?.xScale ?? 1.0
  }
        
}