def kml_cb(mapping):
    """
    Create text for a colorbar png file overlay
    """

    kml_text = """
<ScreenOverlay>
  <name>{name:s}</name>
  <Icon>
    <href>{cb_file:s}</href>
  </Icon>
  <overlayXY x="{xfrac:.4f}" xunits="fraction" y="{yfrac:.4f}" yunits="fraction"/>
  <screenXY x="{xfrac:.4f}" xunits="fraction" y="{yfrac:.4f}" yunits="fraction"/>
</ScreenOverlay>
""".format(**mapping)

    return kml_text