<div dir="ltr"><div>Andrew, the difference between your plots with and without the contour fill layer is surprising. I can only speculate that there might be a branch somewhere inside NCL, that handles antialiasing differently, depending on which graphics layers are active. Notice that the resolution of the lettering is also affected slightly.</div><div><br></div><div>I still think your best bets are to try the resource suggested by Rick, or to avoid the issue by using some form of vector graphics for output. Thanks for showing that contrasting plot, and good luck.</div><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jun 23, 2021 at 8:08 AM Andrew Kren - NOAA Federal <<a href="mailto:andrew.kren@noaa.gov">andrew.kren@noaa.gov</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr">Thanks Dave and Rick. I will try that. Here is what I get on a day when there is nothing on the radar to plot. The highways show up just fine with no changes to the code. I'm wondering if it has something to do with the contours overlaid or something similar? I will also try a PDF or PS file.<div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Jun 22, 2021 at 6:31 PM Dave Allured - NOAA Affiliate <<a href="mailto:dave.allured@noaa.gov" target="_blank">dave.allured@noaa.gov</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>Andrew, PNG is an image format that naturally consists of a grid of pixels. The only pixellation that I see in your plot is the natural pixels in the PNG format. Your highways are mostly very fine diagonal lines. PNG decomposes a diagonal line into a group of small gray and black squares (pixels) on a regularly spaced pixel grid. When the intended line is thin enough, it is difficult to get a clear representation on the pixel grid. One of the possible results is apparently dashed lines like those I am seeing.</div><div><br></div><div>Try making the same plot using vector graphics such as PDF, postscript (PS), or SVG, as Rick suggested. These vector formats preserve a true mathematical representation of line data. The result is clean edges and fine lines that will not pixellate when you zoom in, when using proper viewing software that supports true vector mode display.</div><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Jun 22, 2021 at 12:15 PM Andrew Kren - NOAA Federal via ncl-talk <<a href="mailto:ncl-talk@mailman.ucar.edu" target="_blank">ncl-talk@mailman.ucar.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr">Thanks, I'll check it out. <br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Jun 22, 2021 at 11:25 AM Rick Brownrigg <<a href="mailto:brownrig@ucar.edu" target="_blank">brownrig@ucar.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>Hi Andrew,</div><div><br></div><div>It's odd that you are getting inconsistent results. Do you see the same thing if you write to a PS or PDF file? I don't know what's going on, but it looks like a bit of overzealous anti-aliasing. There's a resource to control whether antialiasing is applied or not:</div><div><br></div><div><a href="https://www.ncl.ucar.edu/Document/Graphics/Resources/wk.shtml" target="_blank">https://www.ncl.ucar.edu/Document/Graphics/Resources/wk.shtml</a></div><div><br></div><div>It's on by default and generally yields better results, but you might experiment with it.</div><div><br></div><div>Wish I had a better answer.</div><div>Rick</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Jun 22, 2021 at 8:45 AM Andrew Kren - NOAA Federal via ncl-talk <<a href="mailto:ncl-talk@mailman.ucar.edu" target="_blank">ncl-talk@mailman.ucar.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hi there,<div><br></div><div>I am plotting radar data and overlaying highways onto the map. I first plot the radar analysis, then overlay the highway information by reading/plotting the shapefile.</div><div><br></div><div>At times, when I view the PNGs, the highways show up as blotched out (lack of detail and pixelated; see attached image). At other times, the highways show up very clear and darker as expected. Is there a reason for this? Below shows a snippet of my code that produces the radar plot and the highway overlay.</div><div><br></div><div> plot = gsn_csm_contour_map(wks,radar,res)<br><br> ; add highway polylines to the map from shapefile<br> plres = True<br> plres@gsLineColor = "grey48"<br> plres@gsLineThicknessF = 0.2<br> id = gsn_add_shapefile_polylines(wks,plot,SHAPE_DIR+"roadtrl020.shp",plres) <br></div><div><br></div><div>Thanks,<br clear="all"><div><br></div>-- <br><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><pre cols="72" style="white-space:pre-wrap;color:rgb(34,34,34);font-family:"arial black",sans-serif"><span style="font-family:arial,helvetica,sans-serif">Andrew Kren
Meteorologist
NOAA's National Weather Service
Raleigh Forecast Office
1005 Capability Drive, Suite 300
Raleigh, North Carolina 27606
voice: 919-326-1035
mailto: <a href="mailto:andrew.kren@noaa.gov" target="_blank">andrew.kren@noaa.gov</a></span><span style="font-family:arial,helvetica,sans-serif">
</span><span style="color:rgb(17,85,204);font-family:arial,helvetica,sans-serif"><a href="http://www.weather.gov/rah" style="color:rgb(17,85,204)" target="_blank">http://www.weather.gov/rah</a></span></pre></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></blockquote></div></blockquote></div></blockquote></div></div></blockquote></div>
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