Filters all IE filters (AlphaImageLoader filter) through a callable.
string $content The CSS:
mixed $callback A PHP callable:
integer $limit Limit the number of replacements:
integer $count Will be populated with the count:
string The filtered CSS
protected function filterIEFilters($content, $callback, $limit = -1, &$count = 0) {
return preg_replace_callback('/src=(["\']?)(?<url>.*?)\\1/', $callback, $content, $limit, $count);
}