return new ImageWriterIterator(it);
return new ImageWriterIterator(it, writerExtension);
  private static Iterator getWritersByFilter(Class type,					     ServiceRegistry.Filter filter)  {    try      {        Iterator it = getRegistry().getServiceProviders(type, filter, true);        return new ImageWriterIterator(it);      }    catch (IllegalArgumentException e)      {        return Collections.EMPTY_SET.iterator();      }  }