To support high-resolution graphics on devices with retina displays, create two versions of each image in your app: a standard size image, and a double-sized image with "@2x" added to the name:
|Standard Size:||High Resolution:|
60 x 20
120 x 40
To refer to an image in your code (or in Interface Builder or Storyboard), use the filename of the standard sized image. iOS will automatically detect and use the @2x version if the device supports it.
imageView.image = [UIImage imageNamed:@"button.png"];