NCL Home >
Documentation >
Functions >
Color routines
RGBtoCmap
Reads a text file of RGB triplets and converts them to a colormap.
Prototype
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl" ; This library is automatically loaded
; from NCL V6.2.0 onward.
; No need for user to explicitly load.
function RGBtoCmap (
filename : string
)
return_val [*][3] : float
Return value
The results are returned in a float array dimensioned nrows x 3, where nrows is the number of rows in the input file.
Description
This function reads a text file of RGB triplets (integers that range from 0 to 255) and converts them to a color map that is dimensioned nrows x 3 (R,G,B). The first triplet is the background color and the second triplet is the foreground color. The RGB values will be normalized (RGB/255). This color map can then be used with a function like gsn_define_colormap to define a color map for a workstation.
Examples
Example 1
Assume you have a file called "rgb.txt" of the following RGB values:
255 255 255 0 0 0 147 112 219 0 0 200 60 100 230 120 155 242 176 224 230The following NCL code will read this file and use it to define a new colormap:
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
begin
cmap = RGBtoCmap("rgb.txt")
wks = gsn_open_wks("x11","test")
gsn_define_colormap(wks,cmap)
gsn_draw_colormap(wks)
end