title: Image resolutions to supply for adaptive iOS app
body: <p>While developing an iOS app I invested a lot of time in making everything adaptive (size-classes and so on). I have implemented an few image scrollers / photo galleries that are screen wide and zoomable. What is the best practice related to multi-screen image storage and exposure?</p>
  
  <p>It is not a problem to store or generate on the fly, let's say, five different resolutions for every image and load the best resolution depending on network connection and screen size. I want to know what is recommended for this sort of diversity.</p>
  
  <p>This is a (perhaps incomplete) list of all the possible image resolutions based on screen size:</p>
  
  <ul>
  <li>iPad landscape &amp; portrait: <strong>704px wide</strong></li>
  <li>iPad 2/3: <strong>694px wide</strong></li>
  <li>iPad 1/2 landscape: <strong>507px wide</strong></li>
  <li>iPad 1/2 portrait: <strong>438px wide</strong></li>
  <li>iPhone 6+: <strong>414px wide</strong></li>
  <li>iPhone 6: <strong>375px wide</strong></li>
  <li>iPhone 4/5 + iPad split screen right-side: <strong>320px wide</strong></li>
  </ul>
  
  <p>All my images are square. So height equals width.</p>
  
  <p>Do I include retina photos or should I use @1x for photos? Do I add extra pixels for the zooming (1.5x max)?</p>