[ncl-talk] saving high resolution plots for publications

Guido Cioni guidocioni at gmail.com
Fri Jul 7 05:12:42 MDT 2017

Answering to both of you. PNG will always have lower resolution since there is no such thing as resolution in PDF. The beauty of vector format consists exactly in this feature: an image is decomposed in different shapes which are drawn every time that the image is shown, depending on the zoom level.

I’m attaching the screenshot of the two images that you provided (PNG and PDF) zoomed-in on my screen (of course it is impossible to put them side to side as they are different formats). In this case also the pdf will look pixelated if you zoom more since I’m attaching a png…the important thing is the difference between the two at the same zoom level!

Your PDF images *may* appear of different “resolution” just because they use less space on the page. You can easily fix this by using the resources gsnMaximize and gsnPaperOrientation or just cut the PDF file with applications such Inkscape. This will produce the best result. 


> Il giorno 07 lug 2017, alle ore 12:54, Barry Lynn <barry.h.lynn at gmail.com> ha scritto:
> Guido:
> Thank you for the tip.
> How do set the NCL script to output in EPS format?
> When I use PDF, I find that the resolution isn't always high enough (especially when I have very small map panels).
> When I blow up the screen, I lose resolution.  This doesn't happen with png.
> Barry
> On Fri, Jul 7, 2017 at 1:17 PM, Guido Cioni <guidocioni at gmail.com <mailto:guidocioni at gmail.com>> wrote:
> I’m going to stop you right there. :) 
> If you’re goal is to produce figures for publications then vector formats like PDF or EPS are preferable (and supported by NCL). They will scale perfectly regardless of a single-column/double-column layout and won’t pixelate. In fact, images that contain lines/points/shapes and combination of the latter ones should always be reproduced in vector format.
> You can use a raster format (PNG, JPEG) only if the image/data you’re publishing is already on raster format (e.g. photos taken with cameras, satellite pictures…). 
> Note that sometimes a PNG with a decent resolution for publication will be larger than a PDF with the same image. Please (!!) don’t use PNG for publications as long as they are not strictly necessary :) :) 
> Cheers
>> Il giorno 07 lug 2017, alle ore 10:51, Sri Nandini <snandini at marum.de <mailto:snandini at marum.de>> ha scritto:
>> Hello
>> Using NCL, i tried the 2 methods for saving my figures as png for publications.
>> 1)The default method   wks =  gsn_open_wks("png", "my figure")
>> And trying to save as 600dpi/optimal resolution
>> 2)  wks_type = "png"
>>    wks_type at wkWidth   =  2500
>>    wks_type at wkHeight  =  2500
>> wks =  gsn_open_wks("png", "my figure")
>> Surprisingly the method 1) yields better sharper resolution figure then method 2).
>> Could someone explain why?
>> Method 3) convert -density 300 (or 600) inputfile.png outfile.png yielded no difference when performed on output of method 1).
>> Any advice would be greatly appreciated.
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