[ncl-talk] Small issue plotting highways
Andrew Kren - NOAA Federal
andrew.kren at noaa.gov
Thu Jun 24 08:27:31 MDT 2021
Thanks. I'm going to try the aliasing, and if that does not work, I'll try
the vector format. I have seen this issue with and without radar data
present on the map. Will keep you updated.
On Thu, Jun 24, 2021 at 10:25 AM Rick Brownrigg <brownrig at ucar.edu> wrote:
> wks at wkAntiAlias = "Off"
>
> http://ncl.ucar.edu/Document/Graphics/Resources/wk.shtml
>
> I'm not sure aliasing is the issue, given your plots with/without radar
> data present. I would think things should be consistently good or bad. Have
> you tried a vector format as David suggested? If you need to post to a web
> page, SVG would be a great option as it scales nicely.
>
> Rick
>
> On Thu, Jun 24, 2021 at 8:18 AM Andrew Kren - NOAA Federal via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> Thanks! I tried that but it did not help. on the anti alias feature, how
>> do I set it? I did not see an example on the ncl documentation pages. I
>> tried this but it did not work. Thanks.
>>
>> wkAntiAlias(wks) = "Off"
>>
>> On Thu, Jun 24, 2021 at 9:24 AM Bassill, Nicholas <nbassill at albany.edu>
>> wrote:
>>
>>> The script can be found here:
>>> https://operations.nysmesonet.org/~nbassill/radar/radar.ncl . As I
>>> said, there's a lot of (fairly poorly commented) stuff going on there, but
>>> the most relatable lines for what you're doing are in the middle:
>>>
>>> countyplot := gsn_csm_contour_map(wks2,newdata,resmap)
>>>
>>> pres = True
>>> pres at gsFillColor = "transparent"
>>> pres at gsFillOpacityF = 0.0
>>> pres at gsEdgesOn = True
>>> pres at gsLineThicknessF = 8.0
>>> pres at gsLineColor= "gray40";"gray30"
>>>
>>> ; if roads.eq."yes"
>>> shpid = gsn_add_shapefile_polylines(wks2,countyplot,"tl_2015_36_prisecroads.shp",pres)
>>> ; end if
>>>
>>> As I mentioned, my line thickness is much greater, though I'm not sure
>>> if that's the reason.
>>>
>>>
>>> Nick Bassill, PhD
>>>
>>> Director of Research & Development, Center Of Excellence
>>>
>>> Affiliated with NYS Mesonet
>>>
>>> LC SB-28, 1400 Washington Ave.,
>>>
>>> SUNY, University at Albany, NY 12222
>>> Contact: (518) 442-6375 | @NickPBassill |
>>> http://operations.nysmesonet.org/~nbassill/
>>> ------------------------------
>>> *From:* Andrew Kren - NOAA Federal <andrew.kren at noaa.gov>
>>> *Sent:* Wednesday, June 23, 2021 6:02 PM
>>> *To:* Bassill, Nicholas <nbassill at albany.edu>
>>> *Cc:* Dave Allured - NOAA Affiliate <dave.allured at noaa.gov>; ncl-talk <
>>> ncl-talk at ucar.edu>
>>> *Subject:* Re: [ncl-talk] Small issue plotting highways
>>>
>>> Sure go ahead and share if you like.
>>>
>>> On Wed, Jun 23, 2021 at 5:21 PM Bassill, Nicholas <nbassill at albany.edu>
>>> wrote:
>>>
>>> Hi Andrew, all,
>>> Sort of a shot in the dark here, but coincidentally, I also regularly
>>> make radar plots and overlay highways (also in gray), along with a whole
>>> bunch of other info and I have not noticed this with my png files. I also
>>> use a shapefile for the highways and more or less use your technique I
>>> think. I'm attaching two examples - one from an active day, and one from
>>> today just to demonstrate that I always see the same road behavior. I see
>>> your line thickness is very small - perhaps increasing the thickness would
>>> help a bit?
>>>
>>> If you'd like I'd be happy to share this script, though fair warning it
>>> has a ton of stuff in so may be a bit hard to parse.
>>>
>>>
>>> Nick Bassill, PhD
>>>
>>> Director of Research & Development, Center Of Excellence
>>>
>>> Affiliated with NYS Mesonet
>>>
>>> LC SB-28, 1400 Washington Ave.,
>>>
>>> SUNY, University at Albany, NY 12222
>>> Contact: (518) 442-6375 | @NickPBassill |
>>> http://operations.nysmesonet.org/~nbassill/
>>> ------------------------------
>>> *From:* ncl-talk <ncl-talk-bounces at mailman.ucar.edu> on behalf of Dave
>>> Allured - NOAA Affiliate via ncl-talk <ncl-talk at mailman.ucar.edu>
>>> *Sent:* Wednesday, June 23, 2021 4:52 PM
>>> *To:* Andrew Kren - NOAA Federal <andrew.kren at noaa.gov>
>>> *Cc:* ncl-talk <ncl-talk at ucar.edu>
>>> *Subject:* Re: [ncl-talk] Small issue plotting highways
>>>
>>> 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.
>>>
>>> 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.
>>>
>>>
>>> On Wed, Jun 23, 2021 at 8:08 AM Andrew Kren - NOAA Federal <
>>> andrew.kren at noaa.gov> wrote:
>>>
>>> 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.
>>>
>>>
>>> On Tue, Jun 22, 2021 at 6:31 PM Dave Allured - NOAA Affiliate <
>>> dave.allured at noaa.gov> wrote:
>>>
>>> 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.
>>>
>>> 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.
>>>
>>>
>>> On Tue, Jun 22, 2021 at 12:15 PM Andrew Kren - NOAA Federal via ncl-talk
>>> <ncl-talk at mailman.ucar.edu> wrote:
>>>
>>> Thanks, I'll check it out.
>>>
>>> On Tue, Jun 22, 2021 at 11:25 AM Rick Brownrigg <brownrig at ucar.edu>
>>> wrote:
>>>
>>> Hi Andrew,
>>>
>>> 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:
>>>
>>> https://www.ncl.ucar.edu/Document/Graphics/Resources/wk.shtml
>>>
>>> It's on by default and generally yields better results, but you might
>>> experiment with it.
>>>
>>> Wish I had a better answer.
>>> Rick
>>>
>>>
>>> On Tue, Jun 22, 2021 at 8:45 AM Andrew Kren - NOAA Federal via ncl-talk <
>>> ncl-talk at mailman.ucar.edu> wrote:
>>>
>>> Hi there,
>>>
>>> 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.
>>>
>>> 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.
>>>
>>> plot = gsn_csm_contour_map(wks,radar,res)
>>>
>>> ; add highway polylines to the map from shapefile
>>> plres = True
>>> plres at gsLineColor = "grey48"
>>> plres at gsLineThicknessF = 0.2
>>> id =
>>> gsn_add_shapefile_polylines(wks,plot,SHAPE_DIR+"roadtrl020.shp",plres)
>>>
>>> Thanks,
>>>
>>> --
>>>
>>> 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: andrew.kren at noaa.govhttp://www.weather.gov/rah
>>>
>>>
>>>
>>> --
>>>
>>> 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: andrew.kren at noaa.govhttp://www.weather.gov/rah
>>>
>>>
>>>
>>
>> --
>>
>> 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: andrew.kren at noaa.govhttp://www.weather.gov/rah
>>
>>
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>
>
--
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: andrew.kren at noaa.govhttp://www.weather.gov/rah
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