A playground to create a UIImageView with a gradient on top of it

ImageViewWithGradient.playground

import UIKit
import AVFoundation


class ImageViewWithGradient: UIImageView
{
  let myGradientLayer: CAGradientLayer
  
  override init(frame: CGRect)
  {
    myGradientLayer = CAGradientLayer()
    super.init(frame: frame)
    self.setup()
  }
  
  required init(coder aDecoder: NSCoder)
  {
    myGradientLayer = CAGradientLayer()
    super.init(coder: aDecoder)
    self.setup()
  }
  
  func setup()
  {
    myGradientLayer.startPoint = CGPoint(x: 0, y: 0)
    myGradientLayer.endPoint = CGPoint(x: 1, y: 1)
    let colors: [CGColorRef] = [
      UIColor.clearColor().CGColor,
      UIColor(red: 0, green: 0, blue: 0, alpha: 0.3).CGColor,
      UIColor(red: 1, green: 1, blue: 1, alpha: 0.5).CGColor,
      UIColor(red: 0, green: 0, blue: 0, alpha: 0.3).CGColor,
      UIColor.clearColor().CGColor ]
    myGradientLayer.colors = colors
    myGradientLayer.opaque = false
    myGradientLayer.locations = [0.0,  0.3, 0.5, 0.7, 1.0]
    self.layer.addSublayer(myGradientLayer)
  }
  
  override func layoutSubviews()
  {
    myGradientLayer.frame = self.layer.bounds
  }
}


var aView = ImageViewWithGradient(frame: CGRect(x: 0, y: 0, width: 500, height: 500))