[geos-devel] GEOSIntersection returns the input

[Giacomo Piva]

Thank you.
Finally I get the intersection by using 2 polygons from linear ring


Jürgen E. Fischer ha scritto:
> Hi Giacomo,
>
> some comments:
>
> On Tue, 25. Aug 2009 at 09:03:47 +0200, Giacomo Piva wrote:
>   
>>    coordseq = (GEOSCoordSeq) GEOSCoordSeq_create(5, 2);   //5 points bi-dimensional
>>     
> [...]
>   
>>    area_1 = GEOSGeom_createLinearRing(coordseq);   
>>     
> [...]
>   
>>    area_2 = GEOSGeom_createLinearRing(coordseq);
>>     
>
> You need a new coordinate sequence here.  GEOSGeom_createLinearRing takes
> ownership of it.
>
>   
>>    intersection = GEOSIntersection(area_1, area_2);
>>     
>
> You're intersecting two rings here.   You might want to GEOSGeom_createPolygon
> from the rings and intersect those.
>
>   
>>    GEOSCoordSeq_destroy(coordseq);
>>     
>
> The coordinate sequence is owner by the linear ring.  So you shouldn't destroy
> it here.
>
>   
>>    coordseq = (GEOSCoordSeq) GEOSCoordSeq_create(2, 2);   //2 points bi-dimensional
>>     
>
> The (pointer to the) coordinate sequence you allocate here is lost...
>
>   
>>        coordseq = (GEOSCoordSeq) GEOSGeom_getCoordSeq(geom);
>>     
>
> ...when you overwrite it here.
>
> hth
> Jürgen
>
>   


-- 
Giacomo