title: Having @2x image assets without @1x assets
body: <p>I'm working on an app which has a lot of graphics.  The app is targeting iPhones with iOS 7+, so all of the devices that support it have retina displays.  I'm adding only @2x and @3x graphics, because @1x graphics are never going to be used, and I don't want the size of the bundle to grow more than it has to.</p>
  
  <p>I load most of the images programmatically:</p>
  
  <pre><code>[self.imageView setImage:[UIImage imageNamed:@"ButtonOn"]];
  </code></pre>
  
  <p>This is supposed to load <code>ButtonOn@2x.jpg</code> for @2x displays and <code>ButtonOn@3x.jpg</code> for iPhone 6 plus.</p>
  
  <p>However, I noticed this behavior:</p>
  
  <ul>
  <li>iPhone 6 Plus does load the @3x image.</li>
  <li>But the other iPhones – 4, 4s, 5s and 6, do not load the @2x.</li>
  <li>I can force it to load the @2x image by using the graphics full name, for instance: <code>[UIImage imageNamed:@"ButtonOn@2x.jpg"]</code>, but this defeats the purpose of the naming convention, and it also forces me to detect the screen density by myself.</li>
  </ul>
  
  <p>Is there a way to have @2x and @3x images without @1x ones?</p>
  
  <p><strong>UPDATE:</strong> the problem had nothing to do with the screen density.  The problem was that, since I am using JPG graphics instead than PNG ones, Xcode can't find them unless I use the file's full name extension.  Maybe this is a bug.</p>