Re: [Matplotlib-users] Get contourf image as array

[David H. <dh...@gm...>]

Thanks Ben. I'll take a look through the archive.

On 10/16/14, 9:43 AM, Benjamin Root wrote:
> What you are looking for is called "rasterization". Matplotlib does this
> deep within the codebase and is not accessible (believe me, I tried).
> However, there have been other discussions in this mailing list about
> how to use GDAL to rasterize a set of polygons (represented as paths),
> including some links to stack-overflow questions. It isn't a complete
> end-to-end solution, but the pieces are there.
>
> Cheers!
> Ben Root
>
>
> On Wed, Oct 15, 2014 at 2:09 PM, David Hoese <dh...@gm...
> <mailto:dh...@gm...>> wrote:
>
>     For the first question, if I save the figure (as a PNG I'm guessing,
>     unless you can save into a more array-like format), I'd have to make
>     sure that there were no labels or ticks and that the axes fit the whole
>     figure. I'd also have to get the dpi and size information correct, but I
>     suppose it would be possible that way. I was hoping for something a
>     little easier and in-memory. This might be the simplest answer the more
>     I think about it.
>
>     If I'm starting from the paths, I'd still have to write them to the
>     "grid" array. I thought maybe the backend could do that and I magically
>     get the image.
>
>     I'll look in to using savefig and getting the data out.
>
>     -Dave
>
>     On 10/15/14, 12:42 PM, Joy merwin monteiro wrote:
>     > pardon the query if it seems dumb, but why don't you do a savefig()
>     > after plotting the data and then convert it to any format you like?
>     >
>     > alternatively, contour() and contourf() both create paths that can
>     > be accessed:
>     >
>     > cf = contourf(.....)
>     >
>     > output = cf.collections.pop()
>     > paths = output.get_paths()[i] # for the various contours
>     >
>     > the x,y coordinates can then be accessed as
>     >
>     > xcoords = paths.vertices.transpose()[0]
>     > ycoords = paths.vertices.transpose()[1]
>     >
>     > you can then do whatever you wish with them.
>     >
>     > Joy
>     >
>     >
>     > On Wed, Oct 15, 2014 at 9:11 PM, David Hoese <dh...@gm... <mailto:dh...@gm...>
>      > <mailto:dh...@gm... <mailto:dh...@gm...>>> wrote:
>      >
>      >     I've been searching and reading through source code and
>     google searches
>      >     to see if this is possible, but no luck so far. I'm basically
>     trying to
>      >     map some data using Basemap, use contourf to map it to an
>     image, and
>      >     then put that image in a geotiff (or other format) for use in
>     other GIS
>      >     programs. I have other tools for remapping data and creating
>     geotiffs,
>      >     but the contour image looks better. All I would need to get
>     this to work
>      >     would be an array representing the image inside the axes of a
>     contourf
>      >     plot. I found a lot of geotiff -> Basemap png results, but I
>     would like
>      >     the reverse.
>      >
>      >     Since the plots are made using paths/patches I'm guessing I
>     would have
>      >     to have a backend render the image and then extract the image
>     somehow.
>      >     Does anyone have some tips or tricks to do something like
>     this? Or am I
>      >     thinking about this completely wrong?
>      >
>      >     Thanks for any help and if you could CC me in any replies it
>     would be
>      >     much appreciated.
>      >
>      >     -Dave
>      >
>      >
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