/* Initializes and uses GEOS internally */
static LWGEOM*
lwpoly_split_by_line(const LWPOLY* lwpoly_in, const LWLINE* blade_in)
{
LWCOLLECTION* out;
GEOSGeometry* g1;
GEOSGeometry* g2;
GEOSGeometry* g1_bounds;
GEOSGeometry* polygons;
const GEOSGeometry *vgeoms[1];
int i,n;
int hasZ = FLAGS_GET_Z(lwpoly_in->flags);
/* Possible outcomes:
*
* 1. The line does not split the polygon
* -> Return a collection with single element
* 2. The line does split the polygon
* -> Return a collection of all elements resulting from the split
*/
initGEOS(lwgeom_geos_error, lwgeom_geos_error);
g1 = LWGEOM2GEOS((LWGEOM*)lwpoly_in);
if ( NULL == g1 )
{
lwerror("LWGEOM2GEOS: %s", lwgeom_geos_errmsg);
return NULL;
}
g1_bounds = GEOSBoundary(g1);
if ( NULL == g1_bounds )
{
GEOSGeom_destroy(g1);
lwerror("GEOSBoundary: %s", lwgeom_geos_errmsg);
return NULL;
}
g2 = LWGEOM2GEOS((LWGEOM*)blade_in);
if ( NULL == g2 )
{
GEOSGeom_destroy(g1);
GEOSGeom_destroy(g1_bounds);
lwerror("LWGEOM2GEOS: %s", lwgeom_geos_errmsg);
return NULL;
}
vgeoms[0] = GEOSUnion(g1_bounds, g2);
if ( NULL == vgeoms[0] )
{
GEOSGeom_destroy(g1);
GEOSGeom_destroy(g2);
GEOSGeom_destroy(g1_bounds);
lwerror("GEOSUnion: %s", lwgeom_geos_errmsg);
return NULL;
}
/* debugging..
lwnotice("Bounds poly: %s",
lwgeom_to_ewkt(GEOS2LWGEOM(g1_bounds, hasZ)));
lwnotice("Line: %s",
lwgeom_to_ewkt(GEOS2LWGEOM(g2, hasZ)));
lwnotice("Noded bounds: %s",
lwgeom_to_ewkt(GEOS2LWGEOM(vgeoms[0], hasZ)));
*/
polygons = GEOSPolygonize(vgeoms, 1);
if ( NULL == polygons )
{
GEOSGeom_destroy(g1);
GEOSGeom_destroy(g2);
GEOSGeom_destroy(g1_bounds);
GEOSGeom_destroy((GEOSGeometry*)vgeoms[0]);
lwerror("GEOSPolygonize: %s", lwgeom_geos_errmsg);
return NULL;
}
#if PARANOIA_LEVEL > 0
if ( GEOSGeometryTypeId(polygons) != COLLECTIONTYPE )
{
GEOSGeom_destroy(g1);
GEOSGeom_destroy(g2);
GEOSGeom_destroy(g1_bounds);
GEOSGeom_destroy((GEOSGeometry*)vgeoms[0]);
GEOSGeom_destroy(polygons);
lwerror("Unexpected return from GEOSpolygonize");
return 0;
}
#endif
/* We should now have all polygons, just skip
* the ones which are in holes of the original
* geometries and return the rest in a collection
*/
n = GEOSGetNumGeometries(polygons);
out = lwcollection_construct_empty(COLLECTIONTYPE, lwpoly_in->srid,
hasZ, 0);
/* Allocate space for all polys */
out->geoms = lwalloc(sizeof(LWGEOM*)*n);
assert(0 == out->ngeoms);
for (i=0; i<n; ++i)
{
GEOSGeometry* pos; /* point on surface */
const GEOSGeometry* p = GEOSGetGeometryN(polygons, i);
int contains;
pos = GEOSPointOnSurface(p);
if ( ! pos )
{
GEOSGeom_destroy(g1);
GEOSGeom_destroy(g2);
GEOSGeom_destroy(g1_bounds);
GEOSGeom_destroy((GEOSGeometry*)vgeoms[0]);
GEOSGeom_destroy(polygons);
lwerror("GEOSPointOnSurface: %s", lwgeom_geos_errmsg);
return NULL;
}
contains = GEOSContains(g1, pos);
if ( 2 == contains )
{
GEOSGeom_destroy(g1);
GEOSGeom_destroy(g2);
GEOSGeom_destroy(g1_bounds);
GEOSGeom_destroy((GEOSGeometry*)vgeoms[0]);
GEOSGeom_destroy(polygons);
GEOSGeom_destroy(pos);
lwerror("GEOSContains: %s", lwgeom_geos_errmsg);
return NULL;
}
GEOSGeom_destroy(pos);
if ( 0 == contains )
{
/* Original geometry doesn't contain
* a point in this ring, must be an hole
*/
continue;
}
out->geoms[out->ngeoms++] = GEOS2LWGEOM(p, hasZ);
}
GEOSGeom_destroy(g1);
GEOSGeom_destroy(g2);
GEOSGeom_destroy(g1_bounds);
GEOSGeom_destroy((GEOSGeometry*)vgeoms[0]);
GEOSGeom_destroy(polygons);
return (LWGEOM*)out;
}
GEOSGeometry*
LWGEOM_GEOS_buildArea(const GEOSGeometry* geom_in)
{
GEOSGeometry *tmp;
GEOSGeometry *geos_result, *shp;
GEOSGeometry const *vgeoms[1];
uint32_t i, ngeoms;
int srid = GEOSGetSRID(geom_in);
vgeoms[0] = geom_in;
geos_result = GEOSPolygonize(vgeoms, 1);
LWDEBUGF(3, "GEOSpolygonize returned @ %p", geos_result);
/* Null return from GEOSpolygonize (an exception) */
if ( ! geos_result ) return 0;
/*
* We should now have a collection
*/
#if PARANOIA_LEVEL > 0
if ( GEOSGeometryTypeId(geos_result) != COLLECTIONTYPE )
{
GEOSGeom_destroy(geos_result);
lwerror("Unexpected return from GEOSpolygonize");
return 0;
}
#endif
ngeoms = GEOSGetNumGeometries(geos_result);
LWDEBUGF(3, "GEOSpolygonize: ngeoms in polygonize output: %d", ngeoms);
LWDEBUGF(3, "GEOSpolygonize: polygonized:%s",
lwgeom_to_ewkt(GEOS2LWGEOM(geos_result, 0)));
/*
* No geometries in collection, early out
*/
if ( ngeoms == 0 )
{
GEOSSetSRID(geos_result, srid);
return geos_result;
}
/*
* Return first geometry if we only have one in collection,
* to avoid the unnecessary Geometry clone below.
*/
if ( ngeoms == 1 )
{
tmp = (GEOSGeometry *)GEOSGetGeometryN(geos_result, 0);
if ( ! tmp )
{
GEOSGeom_destroy(geos_result);
return 0; /* exception */
}
shp = GEOSGeom_clone(tmp);
GEOSGeom_destroy(geos_result); /* only safe after the clone above */
GEOSSetSRID(shp, srid);
return shp;
}
/*
* Iteratively invoke symdifference on outer rings
* as suggested by Carl Anderson:
* postgis-devel/2005-December/001805.html
*/
shp = NULL;
for (i=0; i<ngeoms; ++i)
{
GEOSGeom extring;
GEOSCoordSeq sq;
/*
* Construct a Polygon from geometry i exterior ring
* We don't use GEOSGeom_clone on the ExteriorRing
* due to a bug in CAPI contained in GEOS 2.2 branch
* failing to properly return a LinearRing from
* a LinearRing clone.
*/
sq=GEOSCoordSeq_clone(GEOSGeom_getCoordSeq(
GEOSGetExteriorRing(GEOSGetGeometryN( geos_result, i))
));
extring = GEOSGeom_createPolygon(
GEOSGeom_createLinearRing(sq),
NULL, 0
);
if ( extring == NULL ) /* exception */
{
lwerror("GEOSCreatePolygon threw an exception");
return 0;
}
if ( shp == NULL )
{
shp = extring;
LWDEBUGF(3, "GEOSpolygonize: shp:%s",
lwgeom_to_ewkt(GEOS2LWGEOM(shp, 0)));
}
else
{
tmp = GEOSSymDifference(shp, extring);
LWDEBUGF(3, "GEOSpolygonize: SymDifference(%s, %s):%s",
lwgeom_to_ewkt(GEOS2LWGEOM(shp, 0)),
lwgeom_to_ewkt(GEOS2LWGEOM(extring, 0)),
lwgeom_to_ewkt(GEOS2LWGEOM(tmp, 0))
);
GEOSGeom_destroy(shp);
GEOSGeom_destroy(extring);
shp = tmp;
}
}
GEOSGeom_destroy(geos_result);
GEOSSetSRID(shp, srid);
return shp;
}
GEOSGeometry*
LWGEOM_GEOS_buildArea(const GEOSGeometry* geom_in)
{
GEOSGeometry *tmp;
GEOSGeometry *geos_result, *shp;
GEOSGeometry const *vgeoms[1];
uint32_t i, ngeoms;
int srid = GEOSGetSRID(geom_in);
Face ** geoms;
vgeoms[0] = geom_in;
#ifdef LWGEOM_PROFILE_BUILDAREA
lwnotice("Polygonizing");
#endif
geos_result = GEOSPolygonize(vgeoms, 1);
LWDEBUGF(3, "GEOSpolygonize returned @ %p", geos_result);
/* Null return from GEOSpolygonize (an exception) */
if ( ! geos_result ) return 0;
/*
* We should now have a collection
*/
#if PARANOIA_LEVEL > 0
if ( GEOSGeometryTypeId(geos_result) != COLLECTIONTYPE )
{
GEOSGeom_destroy(geos_result);
lwerror("Unexpected return from GEOSpolygonize");
return 0;
}
#endif
ngeoms = GEOSGetNumGeometries(geos_result);
#ifdef LWGEOM_PROFILE_BUILDAREA
lwnotice("Num geometries from polygonizer: %d", ngeoms);
#endif
LWDEBUGF(3, "GEOSpolygonize: ngeoms in polygonize output: %d", ngeoms);
LWDEBUGF(3, "GEOSpolygonize: polygonized:%s",
lwgeom_to_ewkt(GEOS2LWGEOM(geos_result, 0)));
/*
* No geometries in collection, early out
*/
if ( ngeoms == 0 )
{
GEOSSetSRID(geos_result, srid);
return geos_result;
}
/*
* Return first geometry if we only have one in collection,
* to avoid the unnecessary Geometry clone below.
*/
if ( ngeoms == 1 )
{
tmp = (GEOSGeometry *)GEOSGetGeometryN(geos_result, 0);
if ( ! tmp )
{
GEOSGeom_destroy(geos_result);
return 0; /* exception */
}
shp = GEOSGeom_clone(tmp);
GEOSGeom_destroy(geos_result); /* only safe after the clone above */
GEOSSetSRID(shp, srid);
return shp;
}
LWDEBUGF(2, "Polygonize returned %d geoms", ngeoms);
/*
* Polygonizer returns a polygon for each face in the built topology.
*
* This means that for any face with holes we'll have other faces
* representing each hole. We can imagine a parent-child relationship
* between these faces.
*
* In order to maximize the number of visible rings in output we
* only use those faces which have an even number of parents.
*
* Example:
*
* +---------------+
* | L0 | L0 has no parents
* | +---------+ |
* | | L1 | | L1 is an hole of L0
* | | +---+ | |
* | | |L2 | | | L2 is an hole of L1 (which is an hole of L0)
* | | | | | |
* | | +---+ | |
* | +---------+ |
* | |
* +---------------+
*
* See http://trac.osgeo.org/postgis/ticket/1806
*
*/
#ifdef LWGEOM_PROFILE_BUILDAREA
lwnotice("Preparing face structures");
#endif
/* Prepare face structures for later analysis */
geoms = lwalloc(sizeof(Face**)*ngeoms);
for (i=0; i<ngeoms; ++i)
geoms[i] = newFace(GEOSGetGeometryN(geos_result, i));
#ifdef LWGEOM_PROFILE_BUILDAREA
lwnotice("Finding face holes");
#endif
/* Find faces representing other faces holes */
findFaceHoles(geoms, ngeoms);
#ifdef LWGEOM_PROFILE_BUILDAREA
lwnotice("Colletting even ancestor faces");
#endif
/* Build a MultiPolygon composed only by faces with an
* even number of ancestors */
tmp = collectFacesWithEvenAncestors(geoms, ngeoms);
#ifdef LWGEOM_PROFILE_BUILDAREA
lwnotice("Cleaning up");
#endif
/* Cleanup face structures */
for (i=0; i<ngeoms; ++i) delFace(geoms[i]);
lwfree(geoms);
/* Faces referenced memory owned by geos_result.
* It is safe to destroy geos_result after deleting them. */
GEOSGeom_destroy(geos_result);
#ifdef LWGEOM_PROFILE_BUILDAREA
lwnotice("Self-unioning");
#endif
/* Run a single overlay operation to dissolve shared edges */
shp = GEOSUnionCascaded(tmp);
if ( ! shp )
{
GEOSGeom_destroy(tmp);
return 0; /* exception */
}
#ifdef LWGEOM_PROFILE_BUILDAREA
lwnotice("Final cleanup");
#endif
GEOSGeom_destroy(tmp);
GEOSSetSRID(shp, srid);
return shp;
}
