[ncl-talk] Small issue plotting highways
Rick Brownrigg
brownrig at ucar.edu
Thu Jun 24 08:24:44 MDT 2021
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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