NCL Home > Documentation > Graphics > Graphical Interfaces

gsn_open_wks

Opens a workstation on which to draw graphics.

Prototype

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

	function gsn_open_wks (
		type [1] : string,  
		name [1] : string   
	)

	return_val [1] :  graphic

Arguments

type

The type of workstation to open.

name

The name of the workstation.

Return value

A scalar id of the workstation is returned.

Description

This function creates a workstation for drawing graphics, given a workstation type and name.

The workstation type can be one of "ps", "eps", "epsi" for PostScript output, or "pdf" for PDF output, "png" for PNG file output, "x11" for display to an X11 window, or new with NCL v6.2.0, "svg" for SVG file output . The name will be used for the output file (if applicable) and with the appropriate file suffix appended. For output formats that do not support multiple pages, such as PNG, a sequence number will be included in the suffix when more than one plot is generated.

The new cairo workstation types added in NCL V5.2.0 ("newpdf", "newps", "png") are now the default in V6.1.0. If you specify "ps", "pdf", or "png", you will now be getting the new cairo workstation. In order to get the old PS and PDF workstations, use "oldps" or "oldpdf". The old "x11" driver has also been replaced with the cairo X11 driver. There are no "oldx11" or "oldpng" drivers.

The new cairo "pdf" files are generally smaller than the old "pdf" files, but the opposite is not true for PS files. See below for using resources to alter the default PNG image size).

If a resource file name.res exists, it will be loaded. name can have a directory path as part of its string, if the resource file you want to load is in a separate directory from where the NCL script resides.

As of V6.1.0, the default color map associated with a workstation is "ncl_default". The default color map in V6.0.0 and older was "default".

If you want to change the default color map that NCL uses, you can:

  1. Set an attribute of type called wkColorMap to one of the other predefined color maps.
  2. Create your own.
  3. Permanently change the default color map that is used by setting one in your .hluresfile file.

In V6.1.0, you can now change the color map used by a color contour, vector, or streamline plot by setting one of the new resources: cnFillPalette, vcLevelPalette, and stLevelPalette. Note that these resources have nothing to do with the workstation color map.

If you don't have gsnMaximize set to True (for when you draw your plots), then by default, all output going to a PS or PDF file will be in "portrait" mode. To change this to "landscape" mode, do the following:

   wks_type = "ps"        ; or "pdf"
   wks_type@wkOrientation = "landscape"
   wks = gsn_open_wks(wks_type,"example")

In V5.2.0, you can now specify a paper size, or a paper width and height when you open any one of the PS or PDF workstations:

   wks_type = "pdf"
   wks_type@wkPaperSize = "A4"
   wks = gsn_open_wks(wks_type,"example")

   wks_type = "ps"
   wks_type@wkPaperWidthF  =  8.5  ; in inches
   wks_type@wkPaperHeightF = 14.0  ; in inches
   wks = gsn_open_wks(wks_type,"example")

The default image resolution for PNG output is 1024x1024. If want to import images into a web page, presentation, or poster, you may want to increase this size for better resolution. To change this to 2500 x 2500 for example, use the following:

   wks_type = "png"
   wks_type@wkWidth = 2500
   wks_type@wkHeight = 2500 
   wks = gsn_open_wks(wks_type,"example")

Note that NCL always draws its graphics to a square window. If you set these resources to a non-square, the resultant image will be resized to fit in the largest square of the given rectangle.

You can have up to fifteen PostScript workstations open at one time, but you can only have one NCGM or PDF workstation open at one time.

See Also

gsn_define_colormap, clear, update, frame, NhlUpdateWorkstation, NhlChangeWorkstation

Examples

Try the following script with the resource files zero.res, one.res, two.res, three.res, and four.res in the same directory. Also, try running this script without the resource files to see the difference:

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

begin
  xwks    = gsn_open_wks("x11", "zero")
  ps1wks  = gsn_open_wks("ps",  "one")
  ps2wks  = gsn_open_wks("ps",  "two")
  pdfwks  = gsn_open_wks("pdf", "three")
  ncgmwks = gsn_open_wks("ncgm","four")

  gsn_text_ndc(xwks,   "X workstation",0.5,0.5,False)
  gsn_text_ndc(ps1wks, "PS 1 workstation",0.5,0.5,False)
  gsn_text_ndc(ps2wks, "PS 2 workstation",0.5,0.5,False)
  gsn_text_ndc(pdfwks, "PDF workstation",0.5,0.5,False)
  gsn_text_ndc(ncgmwks,"NCGM workstation",0.5,0.5,False)

  frame(xwks)
  frame(ps1wks)
  frame(ps2wks)
  frame(pdfwks)
  frame(ncgmwks)
end

For some other application examples, see: