title: how to cut a css sprite image like this to make an animation?
body: <p>google shows us a very good example using css sprite to make an animation.</p>
  
  <p><a href="http://www.google.com/green/storyofsend/desktop/#/over-to-google" rel="nofollow">http://www.google.com/green/storyofsend/desktop/#/over-to-google</a> is where you can see how it works(just focus on the envelop).</p>
  
  <p>I just wonder how to make a image like this?
  <a href="http://www.google.com/green/storyofsend/desktop/assets/images/package.png" rel="nofollow">http://www.google.com/green/storyofsend/desktop/assets/images/package.png</a></p>
  
  <p>It's there any tools helping?</p>