title: CSS Sprite generator for Ruby on Rails project
body: <p>I'm currently working on a large, highly trafficked Ruby on Rails website and in order to get our page load times down, we are looking at spriting our background images.  There seem to be a lot of tools out there but many are in the early stages of dev and many don't support some of the features we need.</p>
  
  <p>Features which are important to us:</p>
  
  <ul>
  <li>x or y repeating</li>
  <li>automation with our rake build</li>
  <li>transparency</li>
  <li>generates sprite image and css automatically</li>
  <li>mature</li>
  <li>easy to maintain</li>
  <li>open source</li>
  </ul>
  
  <p>If it was written in Ruby, that would be a bonus but is not essential as long as it can integrate with a rake/cap setup.</p>
  
  <p>Are there any css sprite tools out there which fit most(all?) of these criteria?</p>