Date: Tue Nov 06 2012 - 10:28:32 MST
Hi NCL-team,
While trying to overlay some white/grey clouds over another contour plot we've stumbled over a strange feature. It seems that the overlay is not fully opaque and that the background is actually visible at the contour borders of the overlay. When overlaying light & bright colors over a dark background, this can look pretty annoying.
Are you aware of this feature? Is there any way to avoid it?
Cheers,
Oli
PS. Here an example script which produces the attached image...
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
ni = 101
nj = 101
data = new((/nj,ni/),float)
do j=0,nj-1
do i=0,ni-1
data(j,i) = sqrt(int2flt(i-ni/2)^2 + int2flt(j-nj/2)^2)
end do
end do
data = data/max(data)*3.0
data@_FillValue = -999.0
wks = gsn_open_wks("ps","test")
gsn_merge_colormaps(wks,"topo_15lev","gsdtol")
r = True
r@gsnFrame = False
r@gsnDraw = False
r@cnFillOn = True
r@cnLinesOn = False
r@gsnSpreadColors = True
r@gsnMaximize = True
r@cnLineLabelsOn = False
r@cnLevelSelectionMode= "ManualLevels"
r@cnMinLevelValF = 0.0
r@cnMaxLevelValF = 3.0
r@cnLevelSpacingF = 0.1
pl1 = gsn_contour(wks,data/10.0,r)
data = where(data .gt. 2.0, data@_FillValue, data)
pl2 = gsn_contour(wks,data/2.0+2.0,r)
overlay(pl1,pl2)
draw(pl1)
frame(wks)
delete(wks)
________________________________________
Oliver Fuhrer
Numerical Prediction
Federal Departement of Home Affairs FDHA
Federal Office of Meteorology and Climatology MeteoSwiss
Kraehbuehlstrasse 58, P.O. Box 514, CH-8044 Zurich, Switzerland
Tel. +41 44 256 93 59
Fax +41 44 256 92 78
oliver.fuhrer@meteoswiss.ch
www.meteoswiss.ch - First-hand information
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