title: When UIButton content mode is "center," background image is pixelated
body: <p>Here's how I'm setting the background image and content mode:</p>
  
  <pre><code>[btn setBackgroundImage:[UIImage imageNamed:@"dots_game_horiz_blue.png"] 
                 forState:UIControlStateNormal];
  [btn setContentMode:UIViewContentModeCenter];
  </code></pre>
  
  <p>Is there a reason that the background image would be pixelated? The frame is slightly larger than the image size, and I just want the image to be centered.</p>