title: Unable to generate the derived image using image_style_url
body: <p>Im seeing the following message within Reports when I attempt to use the <a href="http://api.drupal.org/api/drupal/modules!image!image.module/function/image_style_url/7" rel="nofollow">image_style_url</a> function on an image : "Unable to generate the derived image located at public://..."</p>
  
  <p>I have ensured that the directory is under Apache's ownership and I have no problems attaching images for upload to other nodes.</p>
  
  <p>The style name "template" has been set up within the "Image Styles" menu in the Drupal Administration panel. </p>
  
  <p>When the function is called, an image URL is being returned but the image is not displaying because the image is not being created by the server.</p>
  
  <p>Does anyone have any ideas as to how I can fix this issue?</p>
  
  <p>I am simply printing image_style_url, where "thumbnail" is a name given to the image style that was created in the admin area.</p>
  
  <pre><code>$img_url = $node-&gt;field_image[0]['uri'];
  print image_style_url("thumbnail", $img_url);
  </code></pre>