Re: [ferret_users] Customized palette

["William S. Kessler" <william.s.kessler@xxxxxxxx>]

You can write the palette from within Ferret. This is probably not the  
most elegant solution, but it works:

1) make a one-line file in your Ferret path consisting of the line (I  
call it "palette_header"):

RGB_Mapping By_Value

2) make a script in your Ferret path with the following lines (I call  
it "make_centered_palette.jnl"):

sp \rm centered_palette.spk
sp cat palette_header > centered_palette.spk
list/nohead/append/file=centered_palette.spk/format=(4f8.0)  
`vname[i=@min,j=@min,k=@min,l=@min]-1`,`0`,`0`,`80`
list/nohead/append/file=centered_palette.spk/format=(4f8.0)  
`0`,`90`,`90`,`90`
list/nohead/append/file=centered_palette.spk/format=(4f8.0)  
`vname[i=@max,j=@max,k=@max,l=@max]+1`,`80`,`0`,`0`

3) in your Ferret session (or another script), suppose you want to  
shade the variable "rose" (e.g. from etopo20, as I tested):

set dat etopo20
let vname=rose
go make_centered_palette.jnl
pal centered_palette
shade rose

I suppose this will fail if there is no zero in the data being  
shaded ....

Billy K

On Oct 21, 2010, at 1:36 PM, Jian Ma wrote:

> Hi Andy,
>
> Thanks! But that (percentage method) only works when you use
> lev=(-a,a,b). If 0 is not in the middle of your value range, it does  
> not
> work to show 0 as white.
>
> Tony
>
> On Thu, 2010-10-21 at 08:59 -0600, Andy Jacobson wrote:
> > Hi Tony,
> >
> > Did you try light_centered.spk or white_centered.spk?  If you don't  
> > like those, my memory is that you can define a palette with just  
> > three colors (white and the two endpoints), and ferret will  
> > interpolate.
> >
> > -Andy
> >
> >
> > On Wed 20 Oct 2010, at 19:31 , Jian Ma wrote:
> >
> > > Hi All,
> > >
> > > There are 3 methods in Ferret to define new pal files. However, I  
> > > found
> > > no way to define one like this:
> > >
> > > White near 0, dark red on maximum, and blue on minimum.
> > >
> > > I know I can use blue_darkred to achieve this when I have proper  
> > > level
> > > values or change the percentage values in the pal file, but is  
> > > there any
> > > method to make a universal pal file to self adjust correctly about  
> > > 0?
> > >
> > > The last method is to write a fortran program to generate files,  
> > > given
> > > particular level values.
> > >
> > > Many thanks,
> > > Tony