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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
176 224 230
The 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