lwgeom_concavehull()

LWGEOM * lwgeom_concavehull	(	const LWGEOM *	geom,
		double	ratio,
		uint32_t	allow_holes
	)

Take a geometry and build the concave hull.

The concave hull is smaller than the convex hull, but still encompasses all the points of the input. For polygon input the hull encompasses all the input area. For line input the hull encompasses all the input lines.

Parameters

g	the input geometry
ratio	proportion of output vs input
allow_holes	can there be holes in the output. large performance penalty.

Definition at line 1892 of file liblwgeom/lwgeom_geos.c.

{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry *g1, *g3;
        int geosGeomType;
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        geosGeomType = GEOSGeomTypeId(g1);
        if (geosGeomType == GEOS_POLYGON || geosGeomType == GEOS_MULTIPOLYGON) {
                int is_tight = LW_FALSE;
                g3 = GEOSConcaveHullOfPolygons(g1, ratio, is_tight, allow_holes);
        }
        else {
                g3 = GEOSConcaveHull(g1, ratio, allow_holes);
        }
 
        if (!g3)
                GEOS_FREE_AND_FAIL(g1);
 
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g3);
 
        GEOS_FREE(g1, g3);
        return result;
}

References AUTOFIX, LWGEOM::flags, FLAGS_GET_Z, GEOS_FAIL, GEOS_FREE, GEOS_FREE_AND_FAIL, LW_FALSE, LWGEOM2GEOS(), lwgeom_geos_error(), lwnotice(), result, and RESULT_SRID.

Referenced by ST_ConcaveHull().

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