title: Create a custom blur view
body: <p>I need to add a blur view to my app.</p>
  
  <p>I've tried <code>UIBlurEffect</code> but there are just 3 option (Light, Dark, ExtraLight), and I need something between Light and Dark.</p>
  
  <p>I understood the only option I have is to create a custom blur view, but how can I do that?</p>
  
  <p>Any idea?</p>