title: What size should I have my navigationItem.titleView set to?
body: <p>I've been trying to put an image in my <code>titleView</code> in the navigation bar. The image keeps coming out way too blurry and I can't seem to understand why for the life of me. </p>
  
  <p>Right now my images are 28x14 for the @1x, 56x28 for the @2x, 84x42 @3x and the frame of the <code>titleView</code> is 50x50. Should I be sizing the @1x 50px, @2x 100px and the @3x at 150px? Essentially, does the width and height of the image rely on the frame? </p>
  
  <p>I'm not entirely sure how to go about this, any help would be appreciated. I am trying to have the image work for all iPhone sizes, 5,6 and 6 plus. </p>
  
  <p>Code is below: </p>
  
  <pre><code>let imageView: UIImageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
      imageView.image = UIImage(named: "NavigationTitleLogo")
  
      self.navigationItem.titleView = imageView
  </code></pre>
  
  <p><strong>Addition</strong></p>
  
  <p>I'm also having the same issue with my MKAnnotationPin images. </p>