title: Getting images from server for @2x and @3x
body: <p>Lets say that I have an imageView sized with Auto-layout to full width of the screen (which means that the width will be different for iPhone5, iPhone 6 and 6 Plus) and a ratio of 0.5 for the height. The image for this imageView is fetched from a server.</p>
  
  <p>What is the correct way to set the image size for each display (I can store different images for each device, I just can not figure out the correct sizes.</p>
  
  <p>Any explanation ?</p>
  
  <p>Thanks</p>