Swift. Masking a SKTexture on top of a SKSpriteNode

Question

Okay so I have som problems, trying to mask a SKTexture on top op a SKSpriteNode. I've been looking in to SKCropNode, but cant figure it out. (I'm kinda new to this)

How can i mask this SKTexture: (This is the image called "Mask")

on top of this SKSpriteNode:

so its going to turn out like this:

I tried this, but nothing showed up:

picture.size = CGSize(width: menuLine.frame.height, height: menuLine.frame.height)
picture.zPosition = 10

let cropNode = SKCropNode()
cropNode.addChild(picture)
cropNode.maskNode = SKSpriteNode(imageNamed("Mask")
self.addChild(cropNode)
cropNode.position = CGPoint(x: CGRectGetMidX(self.frame), y: CGRectGetMidY(self.frame))
cropNode.zPosition = 10