my @map=(
	sub{(         0,             0,   $_[0] * 255 )},
	sub{(         0,     $_[0]*255,           255 )},
	sub{(         0,           255, (1-$_[0])*255 )},
	sub{( $_[0]*255,           255,             0 )},
	sub{(       255, (1-$_[0])*255,             0 )},
	sub{(       255,             0,     $_[0]*255 )},
	sub{(       255,     $_[0]*255,           255 )},
);
 
sub ramp {
	my( $v, $vmin, $vmax ) = @_;
 
	## Peg $v to $vmax if it is greater than $vmax
	$v = $vmax if $v > $vmax;
	## Or peg $v to $vmin if it is less tahn $vmin.
	$v = $vmin if $v < $vmin;
	## Normalise $v relative to $vmax - $vmin
	$v = 
	( $v    - $vmin ) /
	( $vmax - $vmin ) ;
	## Scale it to the range 0 .. 1784
	$v *= 1785;
 
	my @a = 
	map { int } 
	$map[$v/255]->( ($v % 255) / 256 );
 
	#print join(',',@a)."\n";
 
	return 
	($a[2]<<8 ) |
	($a[1]<<4 ) |
	($a[0]    ) ;
};