title: My Circle Image of Xamarin.forms opacity is not working on Android
body: <p>I have a own android renderer of Image for rounded image on Xamarin.forms. 
  But it's opacity property is not working. 
  When I set it's value, image disappears.</p>
  
  <p>(iOS &amp; Android under Lollipop, works fine)</p>
  
  <p>My renderer is quite similar with this
  <a href="https://github.com/jamesmontemagno/Xamarin.Plugins/tree/master/ImageCircle" rel="nofollow">https://github.com/jamesmontemagno/Xamarin.Plugins/tree/master/ImageCircle</a>
  This package is also not working when I set opacity. </p>
  
  <p>It's really hard to make well working circular image.
  Could you help me?</p>
  
  <p>Thanks.</p>