[ncl-talk] gsMarkerOpacity != 1. and MarkerIndex 16 or 1

[Rick Brownrigg]

Hi Alan,

I see what you mean, and I can't say this is desired behavior.  It
curiously shows up only in the so-called document-based formats (ps, pdf,
svg), but not in the image-based formats (X11, png).  I believe its the
result of the circle's interior is filled, then the border drawn, and where
those two markings overlap, the opacities accumulate.   I unfortunately
don't know offhand how to resolve the problem, nor suggest a work-around. I
will file a bug ticket however.

Rick


On Tue, Dec 2, 2014 at 12:35 PM, Alan Brammer <abrammer at albany.edu> wrote:

> Dear All.
>
> *Problem:  *
> When combining gsMarkerIndex 16 with gsMarkerOpacity < 1.0 a small but
> sometimes significant perimeter circle is drawn with Opacity = 1.0. Leaving
> a bold perimeter around the marker.
> Maybe this is the desired behaviour?
>
>
> *Code and Examples:*
>
> wks = gsn_open_wks("pdf","test")
> res = True
> res at gsnDraw = False
> res at gsnFrame = False
> plot = gsn_blank_plot(wks, res)
> gs_res = True
> gs_res at gsMarkerIndex = 16
> gs_res at gsMarkerSizeF = 0.14
> gs_res at gsMarkerColor = "Red"
> mark1 = gsn_add_polymarker(wks, plot, 0.3, 0.3, gs_res)
> gs_res at gsMarkerOpacityF = 0.6
> mark = gsn_add_polymarker(wks, plot, 0.5, 0.5, gs_res)
> draw(plot)
> frame(wks)
>
> test.pdf   <- zoomed in from the above code. On the semi transparent
> marker the perimeter is evident.  This is normally not noticeable however.
> example.png  <-  map with lots of polymarkers on it.  The bold perimeter
> becomes rather evident in this use.
>
>
> *Solutions?*
> gsLineOpacity does not seem to influence the perimeter line.
>
> I guess I should be using MarkerIndex 1 instead of 16  MarkerIndex 1 also
> does the same thing.  After testing it at the end of this email.
>
>
>
>
> Thanks,
>
> Alan.
>
>
> P.s. Apologies if this comes thru twice, the first version had a pdf which
> was too large.
>
>
>
> --
> Alan Brammer
> PhD Candidate — African Easterly Waves and TC genesis
> University At Albany, NY
> www.atmos.albany.edu/student/abrammer
>
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