title: Symfony2 cssrewrite filter's image paths are way off
body: <p>I'm trying to get Symfony2 to work with jQuery UI. I've gotten the JavaScript portion of it working just fine but I'm having trouble getting the images to work.</p>
  
  <p>One thing I read in the Assetic docs is that the <code>cssrewrite</code> filter can take the image paths in CSS files and update them so the paths point to the right places. This looked like exactly what I needed, so I enabled <code>cssrewrite</code>. Here's how <code>cssrewrite</code> changed my paths:</p>
  
  <pre><code>// original
  images/ui-icons_222222_256x240.png
  
  // using cssrewrite
  ../../../app/Resources/public/css/themes/base/images/ui-icons_222222_256x240.png
  </code></pre>
  
  <p>The first path is no good. The <code>cssrewrite</code> path at least points to the correct path in the filesystem, but relative to my webroot, the <code>cssrewrite</code> path is WAY off. Obviously my <code>app</code> directory is not public.</p>
  
  <p>How do I get the <code>cssrewrite</code> filter to change my paths to something that will actually work?</p>
  
  <p>Here's my stylesheet inclusion. (And yes, I know that the way I'm individually including all these CSS files is dumb, but I'm not worried about that right now.)</p>
  
  <pre><code>    {% stylesheets
          '../app/Resources/public/css/*'
          '../app/Resources/public/css/themes/base/jquery.ui.accordion.css'
          '../app/Resources/public/css/themes/base/jquery.ui.all.css'
          '../app/Resources/public/css/themes/base/jquery.ui.autocomplete.css'
          '../app/Resources/public/css/themes/base/jquery.ui.base.css'
          '../app/Resources/public/css/themes/base/jquery.ui.button.css'
          '../app/Resources/public/css/themes/base/jquery.ui.core.css'
          '../app/Resources/public/css/themes/base/jquery.ui.datepicker.css'
          '../app/Resources/public/css/themes/base/jquery.ui.dialog.css'
          '../app/Resources/public/css/themes/base/jquery.ui.progressbar.css'
          '../app/Resources/public/css/themes/base/jquery.ui.resizable.css'
          '../app/Resources/public/css/themes/base/jquery.ui.selectable.css'
          '../app/Resources/public/css/themes/base/jquery.ui.slider.css'
          '../app/Resources/public/css/themes/base/jquery.ui.tabs.css'
          '../app/Resources/public/css/themes/base/jquery.ui.theme.css'
      %}
          &lt;link rel="stylesheet" href="{{ asset_url }}" /&gt;
      {% endstylesheets %}
  </code></pre>