title: Back button image for UIBarButtonItem has bizarre defect on Retina iPhone display
body: <p>I use the <code>appearance</code> method with UIBarButtonItem to customize the background images of my back button, but on the iPhone Retina display, I see a bizarre issue when using the image.</p>
  
  <p>Here's an example of the non-Retina back button; you'll see that it looks fine:</p>
  
  <p><img src="https://i.stack.imgur.com/cDHj3.png" alt="enter image description here"></p>
  
  <p>However, the Retina version looks off. Appears as though the top few pixels of the image are reappearing down below:</p>
  
  <p><img src="https://i.stack.imgur.com/JquB2.png" alt="enter image description here"></p>
  
  <p>Anyone else seen this before? How did you fix it?</p>
  
  <p>Here's the code I'm using in my appDelegate to customize the UIBarButtonItem's back button:</p>
  
  <pre><code>UIImage *backButton = [[UIImage imageNamed:@"backButton"] resizableImageWithCapInsets:UIEdgeInsetsMake(5, 15, 5,5)];
  
  [[UIBarButtonItem appearance] setBackButtonBackgroundImage:backButton forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
  </code></pre>