title: Retina icons (@2x) aren't being used when images are specified in code
body: <p>I place a play.png image onto my view. When the view initially loads, the iPhone 4 grabs the corresponding play@2x.png file and it looks great. However, when I tap the play button my code swaps it out for the pause.png file. Then, when I tap the pause.png to bring back the play.png it uses the original play.png file (not the @2x version like I thought it would automatically reference).</p>
  
  <p>This is the code I tried to use:</p>
  
  <pre><code>[button setImage:[UIImage imageNamed:@"play.png"] forState:UIControlStateNormal];
  </code></pre>
  
  <p>So, if I swap files after the initial view load, do I have to manually specify the @2x version inside an IF statement? If so, is the UIScreen.scale the best attribute to use for this?</p>
  
  <p>I'm currently using code like this:</p>
  
  <pre><code>if ([UIScreen mainScreen].scale &gt; 1.0) 
  { 
      [button setImage:[UIImage imageNamed:@"play@2x.png"] forState:UIControlStateNormal]; 
  } 
  else 
  { 
      [button setImage:[UIImage imageNamed:@"play.png"] forState:UIControlStateNormal]; 
  }
  </code></pre>
  
  <p>It's working fine but having the IF statement in there is annoying and seems a little fragile.</p>
  
  <p>Thanks in advance to all you smarties out there.</p>