[ncl-talk] question about contour opacities

[Rick Brownrigg]

Hi Will,

Offhand, I would think you could set up a custom colormap that consisted of
RGBa tuples, which were all the same value for the 1st 3 components, and
only the opacity (alpha) channel varied. Something like:

   myColors = new((/100,4/_, float)   ; colormap of 100 values
  do i=0,99
     mColors(i,:) = (/ 0., 0., 1., i / 100. /)   ;; transparent to solid
blues
   end do

Then set either cnFillPalette or cnFillColors to "myColors"

   http://ncl.ucar.edu/Applications/rgbacolor.shtml

Hope that helps...
Rick



On Thu, Mar 25, 2021 at 12:43 AM Will Hobbs via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Hi all
>
>
>
> I suspect the answer is ‘no’, but is it possible to set multiple values
> for cnFillOpacity?
>
>
>
> I’d like to plot an overlay that has a single fill color, but uses opacity
> as it’s ‘colourmap/contour level’.
>
>
>
> I can see a way of doing this by looping through each contour level and
> setting explicit levels/opacities each time, but I wonder if there’s a more
> efficient way.
>
>
>
> Will
>
>
>
> *Will Hobbs *
>
>
>
> Institute for Marine and Antarctic Studies (IMAS)
> University of Tasmania
>
> Private Bag 80, Hobart, 7001, TAS, AUSTRALIA
>
> +61 3 6226 2970
>
> imas.utas.edu.au
>
> aappartnership.org.au
>
>
>
>
>
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