title: Confused about ios image size on different iphone
body: <p>I have a general question about how images are displayed on iphone
  For example iphone 5, 5s support 320x568 points or 640x1136 pixles.
  If I want to create 4 images all same size to take the whole screen when rendered in 5s portrait mode, can I say each image should be 160x284 pixels? 
  Now what if the same app is now rendered in 4s or 6? How the images are displayed? Those 4 160x284 images are still taking the whole screen?</p>
  
  <p>Thanks</p>