BEGIN {
  my @map = (
    ( map rgb2n(      0,       0,      $_), (   0.. 255) ), # => (     0,      0, 0..255)
    ( map rgb2n(      0, $_- 255,     255), ( 256.. 510) ), # => (     0, 1..255,    255)
    ( map rgb2n(      0,     255,  765-$_), ( 511.. 765) ), # => (     0,    255, 254..0)
    ( map rgb2n($_- 765,     255,       0), ( 766..1020) ), # => (1..255,    255,      0)
    ( map rgb2n(    255, 1275-$_,       0), (1021..1275) ), # => (   255, 254..0,      0)
    ( map rgb2n(    255,       0, $_-1275), (1276..1530) ), # => (   255,      0, 1..255)
    ( map rgb2n(    255, $_-1530,     255), (1531..1785) ), # => (   255, 1..255,    255)
  ) ;

  sub colorRamp1785_d {
    my ($v, $vmin, $vmax) = @_;

    return $map[(1785 + 1) * ($v - $vmin) / ($vmax - $vmin)] 
                      if ($v >  $vmin) && ($v < $vmax) ;

    return $map[   0] if ($v <= $vmin) ;
    return $map[1785] ;
  } ;
} ;