
Geometry : 
Subject: Re: [geometry] Ring intersection question
From: Will Lucas (wlucas_at_[hidden])
Date: 20141106 16:26:52
On Thu, Nov 6, 2014 at 3:07 PM, Menelaos Karavelas <
menelaos.karavelas_at_[hidden]> wrote:
> Dear Will,
>
> I tried your polygons and the intersection seems to work.
> Please checkout the attached program, and let us know if you get a similar
> output. The output that I get is:
> MULTIPOLYGON(((75 150,250 150,250 75,75 75,75 150)))
>
> Best,
>
>  m.
>
>
> On 06/11/2014 10:44 Î¼Î¼, Will Lucas wrote:
>
> Hi all,
>
> I have a question regarding the intersection of ring concepts using
> Boost.Geometry. I currently have two overlapping rectangles defined by the
> following WKTs:
>
> POLYGON((75 75,75 175,275 175,275 75,75 75))
> POLYGON((50 50,50 150,250 150,250 50,50 50))
>
> When I perform the intersection of these rectangles, I get the
> intersection points:
>
> POLYGON((75 150,250 75))
>
> The intersection points do not allow me to compute the area correctly
> after the intersection. Is there way to get a fully valid ring/polygon out
> of intersection, so that the area will be equal to the overlapping region?
>
> Thanks!
> Will
>
>
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Menelaos,
Thanks for the quick response! I have tested your code, and it correctly
outputs
MULTIPOLYGON(((75 150,250 150,250 75,75 75,75 150)))
I had to comment out the is_valid calls as I'm running the Ubuntu package
(boost 1.54.0), which doesn't contain that helper method.
I'm guess the problem may be my remapping of the OpenCV datatypes. Here
is what I currently am working with
https://gist.github.com/wlucasDFT/0b8e1e07f34ee7e489c6
Do I need to define a polygon wrapper for the custom Contour type I have?
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