title: UIslider thumb image doesn't start from the beginning
body: <p>I am trying to implement a control to show progress of a video and I am  using a UISlider with a custom thumb image but the thumb image doesn't start from the beginning and it doesn't go till the end as well. </p>
  
  <pre><code>playerProgress = UISlider(frame: CGRectMake((btnImage.size.width + 2 * VideoViewControllerUX.ControlPadding), 0, (screenRect.size.width - (btnImage.size.width + 3 * VideoViewControllerUX.ControlPadding)), btnImage.size.height))
  playerProgress.setThumbImage(UIImage(named: "slider"), forState: UIControlState.Normal)
  playerProgress.maximumValue = 100
  playerProgress.minimumValue = 0
  playerProgress.addTarget(self, action: "playerProgressChanged:", forControlEvents: UIControlEvents.ValueChanged)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/v5QiR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/v5QiR.png" alt="Slider Image 1"></a></p>
  
  <p>I am not sure whats going on.</p>
  
  <ul>
  <li><p>Thumb Image:  </p>
  
  <p><a href="https://i.stack.imgur.com/cpSw3.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cpSw3.png" alt="Thumb Image"></a>  </p></li>
  </ul>