SpriteKit action like "Skew" or "Distort" - swift

Question

Is it possible to create an SKAction for SKSpriteNode in SpriteKit that generates the same effect as "Photoshop" with the Edit->Transform->Distort option?
Example:

Answer 1

I solve with this implementation:
Swift 5
extension SKSpriteNode {
func addSkew(value: CGFloat = -1){
var effectNode = SKEffectNode()
effectNode.shouldRasterize = true
effectNode.shouldEnableEffects = true
effectNode.addChild(SKSpriteNode(texture: texture))
effectNode.zPosition = 1
let transform = CGAffineTransform(a: 1 , b: 0,
c: value, d: 1,
tx: 0 , ty: 0)
let transformFilter = CIFilter(name: "CIAffineTransform")!
transformFilter.setValue(transform, forKey: "inputTransform")
effectNode.filter = transformFilter
addChild(effectNode)
texture = nil
}
}

Answer 2

You can create a skew using a 1x1 warp mesh. This is supported in iOS10.0+.
This extension receives the skew angle in degrees, and distorts around the anchor point of the given sprite.
Swift 4.2
extension SKWarpGeometryGrid {
public static var skewPosGridZero:[float2] {
get {
return [float2(0.0, 0.0), float2(1.0, 0.0),
float2(0.0, 1.0), float2(1.0, 1.0)]
}
}
public static func skewXPosGrid(_ skewX: CGFloat, node:SKSpriteNode? = nil) -> [float2] {
let anchorY:Float = Float(node?.anchorPoint.y ?? 0.5)
var skewPosGrid = skewPosGridZero
let offsetX = Float(tan(skewX.degToRad()) * (node == nil ? 1.0 : (node!.size.height/node!.size.width)) )
skewPosGrid[2][0] += offsetX * (1.0 - anchorY)
skewPosGrid[3][0] += offsetX * (1.0 - anchorY)
skewPosGrid[0][0] -= offsetX * anchorY
skewPosGrid[1][0] -= offsetX * anchorY
return skewPosGrid
}
public static func skewYPosGrid(_ skewY: CGFloat, node:SKSpriteNode? = nil) -> [float2] {
let anchorX:Float = Float(node?.anchorPoint.x ?? 0.5)
var skewPosGrid = skewPosGridZero
let offsetY = Float(tan(skewY.degToRad()) * (node == nil ? 1.0 : (node!.size.width/node!.size.height)) )
skewPosGrid[1][1] += offsetY * (1.0 - anchorX)
skewPosGrid[3][1] += offsetY * (1.0 - anchorX)
skewPosGrid[0][1] -= offsetY * anchorX
skewPosGrid[2][1] -= offsetY * anchorX
return skewPosGrid
}
public static func skewX(_ angle: CGFloat, node:SKSpriteNode? = nil) -> SKWarpGeometryGrid {
return SKWarpGeometryGrid(columns: 1, rows: 1, sourcePositions: skewPosGridZero, destinationPositions: skewXPosGrid(angle, node:node))
}
public static func skewY(_ angle: CGFloat, node:SKSpriteNode? = nil) -> SKWarpGeometryGrid {
return SKWarpGeometryGrid(columns: 1, rows: 1, sourcePositions: skewPosGridZero, destinationPositions: skewYPosGrid(angle, node:node))
}
public static func skewZero() -> SKWarpGeometryGrid {
return SKWarpGeometryGrid(columns: 1, rows: 1)
}
}
Example animation:
let spriteNode = SKSpriteNode(imageNamed: "tex")
spriteNode.anchorPoint = CGPoint(x:0.25, y:1.0)
let skewA = SKWarpGeometryGrid.skewX(-45.0, node: spriteNode)
let skewB = SKWarpGeometryGrid.skewX(45.0, node: spriteNode)
spriteNode.warpGeometry = skewB
if let skewActionA = SKAction.warp(to: skewA, duration: 3.0),
let skewActionB = SKAction.warp(to: skewB, duration: 3.0){
// Individual easing
skewActionA.timingMode = .easeInEaseOut
skewActionB.timingMode = .easeInEaseOut
spriteNode.run(SKAction.repeatForever(SKAction.sequence([skewActionA,skewActionB])))
}

Answer 3

The list of available SKAction's is here: https://developer.apple.com/reference/spritekit/skaction
There is none to do exactly what you describe. Instead, you can export multiple sprite images from a photo editing tool like Photoshop, and use an animation action like class func animate(with: [SKTexture], timePerFrame: TimeInterval).
This is a little more work, but should achieve the desired effect.