使用Xcode的Game模版，在GameViewController.swift中改写
if let scene = SKScene(fileNamed: "GameScene") {
// Set the scale mode to scale to fit the window
scene.size = UIScreen.main.bounds.size.applying(CGAffineTransform(scaleX: UIScreen.main.scale, y: UIScreen.main.scale))
//增加此行，即可获得设备真实像素大小的scene
scene.scaleMode = .aspectFill
// Present the scene
view.presentScene(scene)
}
