title: Removing image background in UIImageView at runtime
body: <p>I have a ball assigned to a UIImageView in Interface Builder.  An IBOutlet from the UIImageView is wired to a corresponding UIViewController.  The image has a white background.  When I assign it to the UIImageView in IB, the background is transparent.  In IB, I have the UIImageView set to a transparent background and aspect fill. </p>
  
  <p>When I assign the UIImageView an image at runtime:</p>
  
  <pre><code>self.ball.image = ballImage; //ballImage is a UIImage
  self.ball.backgroundColor = [UIColor clearColor];
  self.ball.contentMode = UIViewContentModeScaleAspectFill;
  </code></pre>
  
  <p>the UIImageView square has a white background where the ball doesn't display.  Meaning all four corners.  What is the difference that the IB version doesn't show a white background at runtime and the programmatic version does?</p>