CAGradientLayers

그라데이션 배경을 만들수 있는 레이어

class DefaultTopToBottomViewController: UIViewController {

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = view.bounds
        gradientLayer.colors = [UIColor.red.cgColor, UIColor.blue.cgColor]

        view.layer.addSublayer(gradientLayer)
    }
}

Coordinate system

let gradientLayer = CAGradientLayer()
gradientLayer.frame = view.bounds
gradientLayer.colors = [UIColor.red.cgColor, UIColor.blue.cgColor]
gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.0)
gradientLayer.endPoint = CGPoint(x: 1.0, y: 1.0)