title: Circular UIImageView in UITableView without performance hit?
body: <p>I have a <code>UIImageView</code> on each of my <code>UITableView</code> cells, that display a remote image (using <code>SDWebImage</code>). I've done some <code>QuartzCore</code> layer styling to the image view, as such:</p>
  
  <pre><code>UIImageView *itemImageView = (UIImageView *)[cell viewWithTag:100];
      itemImageView.layer.borderWidth = 1.0f;
      itemImageView.layer.borderColor = [UIColor concreteColor].CGColor;
      itemImageView.layer.masksToBounds = NO;
      itemImageView.clipsToBounds = YES;
  </code></pre>
  
  <p>So now I have a 50x50 square with a faint grey border, but I'd like to make it circular instead of squared. The app <code>Hemoglobe</code> uses circular images in table views, and that's the effect I'd like to achieve. However, I don't want to use <code>cornerRadius</code>, as that degrades my scrolling FPS. </p>
  
  <p>Here's <code>Hemoglobe</code> showing circular <code>UIImageViews</code>: </p>
  
  <p><img src="https://i.stack.imgur.com/TOh0K.jpg" alt="enter image description here"></p>
  
  <p>Is there any way to get this effect? Thanks.</p>