code: public static String fill(int color) {
      final String colorCode = Integer.toHexString(color & 0xFFFFFF); // Strip alpha
      return FILTER_FILL + "(" + colorCode + ")";
    }
docs: This filter permit to return an image sized exactly as requested wherever is its ratio by
  filling with chosen color the missing parts. Usually used with "fit-in" or "adaptive-fit-in"
  
  @param color integer representation of color.