title: Best practice/tool for AJAX loading indicator as animated PNG sprite?
body: <p>Obviously GIFs do not support an alpha channel. If I waned an alpha-channel capable “throbber,” “spinner,” or Ajax loading indicator, it seems the only (post-IE6) cross-browser option would be a sprited PNG containing all the states of the throbber.</p>
  
  <p>I guess I would be animating it myself using JavaScript to advance the frames (using <code>requestAnimationFrame</code> when available) by changing a class or something that sets the background origin.</p>
  
  <p>I can't seem to find anything that helps generate this, specifically. Does anyone know of any? Any best practices I should know about? (I know that e.g. Compass has a sprite helper I can take advantage of for automating the CSS portion, at least.)</p>