Re: [Matplotlib-users] fill question

[John H. <jdh...@ac...>]

>>>>> "Jeff" == Jeff Whitaker <js...@fa...> writes:

    Jeff> I'm currently working on a map plotting module.  I've added
    Jeff> the ability to plot filled continents on various map
    Jeff> projections, using the GSHHS coastline polygon dataset
    Jeff> (http://www.soest.hawaii.edu/wessel/gshhs/gshhs.html).  This
    Jeff> dataset provides polygon segments that define continental
    Jeff> outlines.  However, before I post it here I'd like to also
    Jeff> provide the capability to fill the 'wet' areas as well.  In
    Jeff> order to do this I need to figure out how to fill the area
    Jeff> between the polygons.  Looks like this module
    Jeff> (http://www.dezentral.de/soft/Polygon/index.html) would do
    Jeff> the trick, but it requires the generaly polygon clipping C
    Jeff> library.  Do you have any suggestions?

agg actually includes a wrapper for gpc, as well as the gpc code
itself, but gpc is GPLd and I haven't included it in matplotlib for
that reason.  Agg separately implements a "scanline boolean algebra"
which I haven't studied in detail but which I understand basically
does the same thing: allow clipping to arbitrary polygons, and
supports boolean operations on polygons --
http://www.antigrain.com/demo/index.html#PAGE_DEMO_scanline_boolean

We have to expose the functionality such that it is available for use
by other backends, much as we use agg for image across backends.

If this is an area that you want to dive into, by all means.
Otherwise, it's on the list of things to do (I just added it to the
goals page in my tree, so it will appear on the site docs in the
not-too-distant-future.

JDH