Zooming and scrolling in SpriteKit

Question

I am new to SpriteKit. I need to display an image via UIImageView OR SpriteNode (it is a background image for a game). However, I need the user to be able to zoom in to the

Answer 1

If you are using an SKCameraNode you can calculate the difference between two touches to define zooming and panning at once.

• Define an SKCameraNode for your SKView
• Check if there are two touches
• If so, calculate the difference between the previous touches and current touches
• Tell the camera to scale by that much
• Pan by the camera by either the average of the two points, or the first one (if there's only one)

Result should be something like this. Note that I used the event?.allTouches instead of the received set, if one finger doesn't move between touches, it's not in the touches set, which would cause a pan where a user would expect a zoom.

let cameraNode = SKCameraNode()

override func didMove(to view: SKView) {

    cameraNode.position = CGPoint(x: size.width / 2, y: size.height / 2)
    addChild(cameraNode)
    camera = cameraNode
}

override func touchesMoved(_ touch: Set, with event: UIEvent?) {

    guard let touches = event?.allTouches else {
        return
    }

    let arr = Array(touches)
    guard let touch = arr.first else {
        return
    }

    var positionInScene = touch.location(in: self)
    var previousPosition = touch.previousLocation(in: self)

    if touches.count > 1 {

        let touch2 = arr[1]

        let positionInScene2 = touch2.location(in: self)
        let previousPosition2 = touch2.previousLocation(in: self)

        let oldDistance = distance(previousPosition, previousPosition2)
        let newDistance = distance(positionInScene, positionInScene2)

        let diff = (oldDistance / newDistance)

        if diff.isNormal && diff != 1 {

            let scaleAction = SKAction.scale(by: diff, duration: 0)
            cameraNode.run(scaleAction)
        }

        previousPosition = average(previousPosition, previousPosition2)
        positionInScene = average(positionInScene, positionInScene2)
    }

    let translation = CGPoint(x: positionInScene.x - previousPosition.x, y: positionInScene.y - previousPosition.y)

    let panAction = SKAction.moveBy(x: -translation.x, y: -translation.y, duration: 0)
    cameraNode.run(panAction)
}

func average(_ a: CGPoint, _ b: CGPoint) -> CGPoint {

    return CGPoint(x: (a.x + b.x) / 2, y: (a.y + b.y) / 2)
}

func distance(_ a: CGPoint, _ b: CGPoint) -> CGFloat {

    let xDist = a.x - b.x
    let yDist = a.y - b.y
    return CGFloat(sqrt((xDist * xDist) + (yDist * yDist)))
}