docs: public static Filter handleURL(ParsedURL url) {
      if(LOG.isDebuggingFiner()) {
        LOG.debugFiner("handleURL " + url.toString());
      }
      if(!isCompatibleURLStatic(url)) {
        return null;
      }
      int id;
      try {
        id = ParseUtil.parseIntBase10(url.getPath());
      }
      catch(NumberFormatException e) {
        return null;
      }
      SoftReference<RenderedImage> ref = images.get(id);
      if(ref != null) {
        RenderedImage ri = ref.get();
        if(ri == null) {
          LOG.warning("Referenced image has expired from the cache!");
        }
        else {
          return new RedRable(GraphicsUtil.wrap(ri));
        }
      }
      // Image not found in registry.
      return null;
    }