title: Fastest way (performance wise) to darken UIView or CALayer
body: <p>I have a UIView / CALayer which I would like to darken. How can I as fast as possible darken it? Is there any way to avoid blending?</p>
  
  <p>Following alternatives is known to me</p>
  
  <ul>
  <li>create a non-opaque CALayer and set background color and opacity and add it as a sublayer above main layer</li>
  <li>same as above using UIView (can be a tad slower...?)</li>
  <li>render view/layer to UIImage and doing drawing with CoreGraphics (is way too slow and content is dynamic/changing)</li>
  </ul>