Re: [ferret_users] About color palette

[Ryo Furue <furue@xxxxxxxxxx>]

Hi Weipeng,

| I want to plot a figure with the value range from -10 to +10 and I 
| prefer to use the grayscale palette and have the white in the center:
| 
| like -10 to 0 ( from darkgray to white)
|      0 to +10 ( from white to darkgray)

A quick and dirty way is

   fill/palette=inverse_grayscale/lev=(0,10,2) abs(var)

where "var" is the variable you want to plot.  This method may be
sufficient for quicklook, but it won't give you a correct color bar.

A palette file that you need may look like

  ! dark gray -> white -> white -> dark gray
  !
    0      20  20  20
    44.001 100 100 100
    55.999 100 100 100
    100    20  20  20

(R,G,B) = (20,20,20) is a dark gray and (R,G,B) = (100,100,100) is
pure white.  The leftmost column is the range of your variable
expressed in percentage; that is, 0% is your smallest value and 100%
is your largest value.

Hope this makes sense.

Ryo