title: Find height and width of a WKInterfaceImage
body: <p>I want to programmatically render a <code>UIImage</code> and then display it on Apple Watch in a <code>WKInterfaceImage</code>, which height and width I set to "Relative to Container" (so that it basically takes up the entire screen space).
  How can I obtain the <code>WKInterfaceImage</code>'s width and and height? As far as I can see, there is no <code>frame</code>-, <code>border</code>- oder <code>layer</code>-property I can access from my extension's code. So what is the proper way to get this information?</p>
  
  <p>Weird enough I have found out that there is a setWidth and setHeight method, but I can't find according getter methods.</p>
  
  <p>At the end of the day I am basically looking for the Watch Kit equivalent to this:</p>
  
  <pre><code>@IBOutlet weak var imageView: UIImageView!
  //...
  var width = imageView.frame.width
  var height = imageView.frame.height
  </code></pre>