[geos-devel] C-API Question about GEOSPolygonize()
woodbri at swoodbridge.com
Tue May 9 22:20:41 EDT 2006
With only the geos_c.h as doc for the C-API and getting totally lost in
the doxygen doc. I thought I would just ask:
It seems from testing, that GEOSPolygonize() always returns a geometry
collection. Is this true? If not what can I expect as the range of
GEOSGeomTypeId that I can expect to get back.
Assuming it is a geometry collection, what can I expect to find in the
collection. Only GEOS_POLYGON, or others like GEOS_MULTIPOLYGON and/or
How does one get the individual polygons out of a GEOS_MULTIPOLYGON? I
would have thought to use:
extern int GEOS_DLL GEOSGetNumGeometries(const GEOSGeom g1);
* Return NULL on exception, Geometry must be a Collection.
* Returned object is a pointer to internal storage:
* it must NOT be destroyed directly.
extern const GEOSGeom GEOS_DLL GEOSGetGeometryN(const GEOSGeom g, int n);
/* Return -1 on exception */
But the comment seems to imply that that is not the correct tool.
What I am trying to do is load a bunch of polylines into linestrings and
feed them to GEOSPolygonize then load the results into polygon
shapefiles. I would like the shapefiles to be able to be loaded into
postGIS as valid polygons if I need to do that later.
Any thoughts, help, advice, sample code pointers, etc would be appreciated.
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