NCL graphic output size and margin problem

Hi All,

I'm trying to output a png figure, however the white margin of the figure is too large (as the attached figure showing). Is there any method to minimize the white margin area? I use the following resources:
  wtype = "png"
  wtype@wkWidth = 2500
  wtype@wkWidth = 2500
  wks = gsn_open_wks(wtype,"ninocorrT")
gsn_define_colormap(wks,"BlueWhiteOrangeRed")

   res@mpFillOn = False
   res@cnFillOn = True
   res@cnLinesOn = False
   res@gsnSpreadColors = True
   res@gsnSpreadColors = True
   res@lbLabelAutoStride = True
contour = gsn_csm_contour_map(wks,crr,res)

I also tried

res@gsnMaximize = True and
res@mpShapeMode = "FreeAspect" and
res@gsnMaximize = True

but it seems that none of them can address this problem.
Does anybody have any idea about this issue?

thanks,
Bo

_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk