title: Implement UITouchDown for UIImageView
body: <p>I know how to implement <code>touchesBegan</code> for <code>UIImageView</code></p>
  
  <p>is it possible to implement <code>UITouchDown</code> for <code>UIImageView</code> ?(i know that i can use <code>touchesBegan</code> instead of <code>UITouchDown</code> but i want to implement <code>UITouchDown</code>)</p>