TableView background keeps white - ios

Question

I'm having a problem with my parallax effect. I'm having a tableView and a ImageView above the tableView. Now when the user scrolls from the top I want to stretch the image a bit. But the problem is that my tableView keeps having a white background like you can see on the screenshot. So the image isn't visible. The screenshot is taken when the viewcontroller loads and then I just pull down as far as I can go. The tableView has backgroundColor .clear so I don't why it isn't working.
My code:
import UIKit
import PureLayout
class ViewController: UIViewController {
lazy var headerImageView: UIImageView = {
let imageView = UIImageView(forAutoLayout: ())
imageView.image = UIImage(named: "test")
imageView.contentMode = .scaleAspectFill
imageView.clipsToBounds = true
return imageView
}()
lazy var tableView: UITableView = {
let tableView = UITableView(forAutoLayout: ())
tableView.delegate = self
tableView.dataSource = self
tableView.separatorStyle = .none
tableView.isOpaque = false
tableView.backgroundColor = .clear
tableView.register(UITableViewCell.self, forCellReuseIdentifier: "default")
tableView.tableFooterView = UIView()
tableView.showsVerticalScrollIndicator = false
return tableView
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(self.headerImageView)
self.headerImageView.autoPinEdge(toSuperviewEdge: .left)
self.headerImageView.autoPinEdge(toSuperviewEdge: .right)
self.headerImageView.autoPin(toTopLayoutGuideOf: self, withInset: 0)
self.headerImageView.autoSetDimension(.height, toSize: 100)
self.view.addSubview(self.tableView)
self.tableView.autoPinEdge(toSuperviewEdge: .left)
self.tableView.autoPinEdge(toSuperviewEdge: .right)
self.tableView.autoPinEdge(toSuperviewEdge: .bottom)
self.tableView.autoPinEdge(.top, to: .bottom, of: self.headerImageView)
}
}
extension ViewController: UITableViewDelegate, UITableViewDataSource {
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 20
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "default", for: indexPath)
cell.textLabel?.text = "test"
cell.backgroundColor = .red
return cell
}
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return 50
}
}
extension ViewController: UIScrollViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
// Parallax functionality
let yOffset = scrollView.contentOffset.y * 0.2
let availableOffset = min(yOffset, 60)
let contentRectYOffset = availableOffset / self.headerImageView.frame.size.height
self.headerImageView.layer.contentsRect = CGRect(x: 0.0, y: contentRectYOffset, width: 1, height: 1)
}
}