b_data-color">$data = one_color($rgb_data,$color)</a></li>
      <li><a href="#data-read_png-filename">$data = read_png($filename);</a></li>
      <li><a href="#write_png-data-filename">write_png($data,$filename);</a></li>
      <li><a href="#A.-bit_planes-bit_plane-data-type">A. @bit_planes = bit_plane($data,$type);</a></li>
      <li><a href="#B.-bit_planes-bit_plane_array-data-type">B. $bit_planes = bit_plane_array($data,$type)</a></li>
      <li><a href="#A.-red-green-blue-rgb-data">A. ($red,$green,$blu