title: CIFilter not working
body: <p>I'm trying to add a blur effect to a layer with following code.<br>
   But it doesn't work, any advise?</p>
  
  <pre><code>let layer = CALayer()
  layer.frame = CGRect(x: 150, y: 150, width: 150, height: 150)
  layer.backgroundColor = UIColor.blue.cgColor
  layer.contents = UIImage(named: "D1")?.cgImage
  
  if let filter = CIFilter(name: "CIGaussianBlur", withInputParameters: ["inputRadius": 15]) {
  filter.setDefaults()
  layer.filters = [filter]
  }
  view.layer.addSublayer(layer)
  </code></pre>
  
  <p>It just displayed the image without filter effect. I'm really confused. Thank you for any advise.</p>