ST_LargestEmptyCircle()

Datum ST_LargestEmptyCircle

(

PG_FUNCTION_ARGS

)

Definition at line 391 of file postgis/lwgeom_geos.c.

{
#if POSTGIS_GEOS_VERSION < 30900
 
        lwpgerror("The GEOS version this PostGIS binary "
                  "was compiled against (%d) doesn't support "
                  "'GEOSMaximumInscribedCircle' function (3.9.0+ required)",
                  POSTGIS_GEOS_VERSION);
                  PG_RETURN_NULL();
 
#else /* POSTGIS_GEOS_VERSION >= 30900 */
        GSERIALIZED* geom;
        GSERIALIZED* boundary;
        GSERIALIZED* center;
        GSERIALIZED* nearest;
        TupleDesc resultTupleDesc;
        HeapTuple resultTuple;
        Datum result;
        Datum result_values[3];
        bool result_is_null[3];
        double radius = 0.0, tolerance = 0.0;
        int32 srid = SRID_UNKNOWN;
        bool is3d = false, hasBoundary = false;
 
        if (PG_ARGISNULL(0))
                PG_RETURN_NULL();
 
        geom = PG_GETARG_GSERIALIZED_P(0);
        tolerance = PG_GETARG_FLOAT8(1);
        boundary = PG_GETARG_GSERIALIZED_P(2);
        srid = gserialized_get_srid(geom);
        is3d = gserialized_has_z(geom);
 
        if (boundary && ! gserialized_is_empty(boundary))
                hasBoundary = true;
 
    /* Empty geometry?  Return POINT EMPTY with zero radius */
        if (gserialized_is_empty(geom))
        {
                LWGEOM* lwcenter = (LWGEOM*) lwpoint_construct_empty(gserialized_get_srid(geom), LW_FALSE, LW_FALSE);
                LWGEOM* lwnearest = (LWGEOM*) lwpoint_construct_empty(gserialized_get_srid(geom), LW_FALSE, LW_FALSE);
                center = geometry_serialize(lwcenter);
                nearest = geometry_serialize(lwnearest);
                radius = 0.0;
        }
        else
        {
                GEOSGeometry *ginput, *gcircle, *gcenter, *gnearest;
                GEOSGeometry *gboundary = NULL;
                double width, height, size;
                GBOX gbox;
                LWGEOM *lwg;
                lwg = lwgeom_from_gserialized(geom);
                if (!lwgeom_isfinite(lwg))
                {
                        lwpgerror("Geometry contains invalid coordinates");
                        PG_RETURN_NULL();
                }
                lwgeom_free(lwg);
 
 
                if (!gserialized_get_gbox_p(geom, &gbox))
                        PG_RETURN_NULL();
 
                if (tolerance <= 0)
                {
                        width = gbox.xmax - gbox.xmin;
                        height = gbox.ymax - gbox.ymin;
                        size = width > height ? width : height;
                        tolerance = size / 1000.0;
                }
 
                initGEOS(lwpgnotice, lwgeom_geos_error);
 
                ginput = POSTGIS2GEOS(geom);
                if (!ginput)
                        HANDLE_GEOS_ERROR("Geometry could not be converted to GEOS");
 
                if (hasBoundary)
                {
                        gboundary = POSTGIS2GEOS(boundary);
                        if (!gboundary)
                                HANDLE_GEOS_ERROR("Boundary could not be converted to GEOS");
                }
 
                gcircle = GEOSLargestEmptyCircle(ginput, gboundary, tolerance);
                if (!gcircle)
                {
                        lwpgerror("Error calculating GEOSLargestEmptyCircle.");
                        GEOSGeom_destroy(ginput);
                        PG_RETURN_NULL();
                }
 
                gcenter = GEOSGeomGetStartPoint(gcircle);
                gnearest = GEOSGeomGetEndPoint(gcircle);
                GEOSDistance(gcenter, gnearest, &radius);
                GEOSSetSRID(gcenter, srid);
                GEOSSetSRID(gnearest, srid);
 
                center = GEOS2POSTGIS(gcenter, is3d);
                nearest = GEOS2POSTGIS(gnearest, is3d);
                GEOSGeom_destroy(gcenter);
                GEOSGeom_destroy(gnearest);
                GEOSGeom_destroy(gcircle);
                GEOSGeom_destroy(ginput);
                if (gboundary) GEOSGeom_destroy(gboundary);
        }
 
        get_call_result_type(fcinfo, NULL, &resultTupleDesc);
        BlessTupleDesc(resultTupleDesc);
 
        result_values[0] = PointerGetDatum(center);
        result_is_null[0] = false;
        result_values[1] = PointerGetDatum(nearest);
        result_is_null[1] = false;
        result_values[2] = Float8GetDatum(radius);
        result_is_null[2] = false;
        resultTuple = heap_form_tuple(resultTupleDesc, result_values, result_is_null);
 
        result = HeapTupleGetDatum(resultTuple);
 
        PG_RETURN_DATUM(result);
 
#endif /* POSTGIS_GEOS_VERSION >= 30900 */
}

References boundary(), GEOS2POSTGIS(), gserialized_get_gbox_p(), gserialized_get_srid(), gserialized_has_z(), gserialized_is_empty(), HANDLE_GEOS_ERROR, LW_FALSE, lwgeom_free(), lwgeom_from_gserialized(), lwgeom_geos_error(), lwgeom_isfinite(), lwpoint_construct_empty(), POSTGIS2GEOS(), POSTGIS_GEOS_VERSION, result, SRID_UNKNOWN, GBOX::xmax, GBOX::xmin, GBOX::ymax, and GBOX::ymin.

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