title: Transparent blurred view is not working
body: <p>I'd like to apply layer on top of ImageView that slightly blurrs it.
  I put a view on top of imageView, subclass it as follows:</p>
  
  <pre><code>class BlurredView: UIView {
  override func draw(_ rect: CGRect) {
      self.backgroundColor = UIColor.clear
      let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.extraLight)
      let blurEffectView = UIVisualEffectView(effect: blurEffect)
      blurEffectView.backgroundColor = UIColor.clear
      blurEffectView.frame = self.bounds
      blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
      self.addSubview(blurEffectView)
     }
  }
  </code></pre>
  
  <p>The result is quite different from what I expected.</p>
  
  <p><a href="https://i.stack.imgur.com/DNKSX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DNKSX.png" alt="enter image description here"></a></p>
  
  <p>How to customize it to make this blur much lighter, so the picture still shows some details? </p>