NhlFreeColor

Removes one or more color entries from one or more workstations.

Prototype

	procedure NhlFreeColor (
		workstations [*] : graphic,  
		color_index  [*] : integer   
	)

Arguments

An array of NCL Workstation identifiers. The identifiers are ones returned either from calling gsn_open_wks or calling create to create a Workstation object.

An array of integer color indexes (between 0 and 255) to be freed.

Description

The NhlFreeColor procedure frees each color index in color_index from the color map of each workstation in the workstations parameter.

See Also

NhlSetColor, NhlNewColor, NhlIsAllocatedColor, NhlGetNamedColorIndex

Examples

Example 1

This example draws a filled contour plot over a map. It uses a "rainbow" colormap which has no gray in it. This causes the continents to be drawn in white. The NhlSetColor procedure is used to add gray to the end of the colormap. This example also shows how to remove this color using NhlFreeColor, and how it affects your plot.

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"

begin
  datadir  = ncargpath("data")
  datafile = datadir + "/cdf/meccatemp.cdf"
;
; Load a file record from the netCDF file
; as a read only data set.
;
  n = addfile(datafile,"r")
  t = n->t(0,:,:)

  type                   = "x11"
  type@wkColorMap        = "rainbow"
  type@wkBackgroundColor = "white"
  type@wkForegroundColor = "black"

  wks = gsn_open_wks(type,"annotation")     ; Open a workstation.
;
; If you don't set this color index, your continent colors
; will be white instead of gray.  First, retrieve the length
; of the colormap, so we can add this color after the last one.
;
  getvalues wks
    "wkColorMapLen" : len
  end getvalues

  NhlSetColor(wks,len,0.8,0.8,0.8)

;
; Set some resources.
;
  res                     = True
  res@gsnSpreadColors     = True
  res@gsnSpreadColorEnd   = -2
  res@gsnMaximize         = True
  res@gsnAddCyclic        = False

  res@cnLevelSelectionMode= "ManualLevels"
  res@cnMinLevelValF      =  195.0
  res@cnMaxLevelValF      =  328.0
  res@cnLevelSpacingF     = 2.25
  res@cnFillOn            = True
  res@cnLinesOn           = False

  res@mpGridAndLimbOn     = False
  res@mpFillDrawOrder     = "PostDraw"

  plot = gsn_csm_contour_map(wks,t,res)

;
; Now remove this color and see how it affects the plot.
;
  NhlFreeColor(wks,190)
  plot = gsn_csm_contour_map(wks,t,res)
end