[ferret_users] Ferret color palette by values...

[Charles Seman <Charles.Seman@xxxxxxxx>]

Dear ferret users,

I have a question about making and using a color palette using 
"RGB_Mapping By_Value" for plotting bias values such that there is color 
white within a range surrounding zero bias and rainbow-like colors by 
value outside of this range.  With a color palette using a single "0" 
level for white and contour levels [-.25,.25] the plot shows no white, 
but by "shifting" the color palette to a "negative" bias (as shown here 
below), we get a white area as desired between [-.25,.25]... Does the 
"interpolation" for shading between contour levels [-.25,.25] use the 
"lower" palette interval limit in question for the interpolation?  so 
that for [-.25,.25], -0.25 is used?  That is, are the RGB values for 
[-0.5,0.0] in the table used to interpolate to -0.25, and then the 
resulting RGB triplet used for specifying the (white) color for the  
[-.25,.25] interval?
!----------------------
! Val   R     G     B
!----------------------

-12.0    0.  100.  100.
-5.0   20.   20.  100.
-2.0   60.   60.  100.
-0.5  100.  100.  100.
0.0  100.  100.  100.
1.0  100.   60.   60.
3.0  100.   20.   20.
10.0  100.  100.    0.

Thanks for your help with this,
Chuck

--

Please note that Charles.Seman@xxxxxxxx should be considered my NOAA
email address, not cjs@xxxxxxxxxxxxxx

********************************************************************
Charles Seman                                Charles.Seman@xxxxxxxx
U.S. Department of Commerce / NOAA / OAR
Geophysical Fluid Dynamics Laboratory         voice: (609) 452-6547
201 Forrestal Road                              fax: (609) 987-5063
Princeton, NJ  08540-6649            http://www.gfdl.noaa.gov/~cjs/
********************************************************************

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