 already
      handled by the core library</li>
  </ul>
  <p>
    The first item means that, for example, image viewers that want to
    handle multiple files can cache decoding information in order to
    speedup the work required to display a TIFF image.
  </p>
  <p>
    The second item is the main reason for this interface.  By interposing
    a "put method" (the routine that is called to pack pixel data in
    the raster) it is possible share the core logic that understands how
    to deal with TIFF whi