ST_AsMVTGeom()

Datum ST_AsMVTGeom

(

PG_FUNCTION_ARGS

)

Definition at line 42 of file lwgeom_out_mvt.c.

{
#ifndef HAVE_LIBPROTOBUF
        elog(ERROR, "ST_AsMVTGeom: Compiled without protobuf-c support");
        PG_RETURN_NULL();
#else
        GBOX *bounds = NULL;
        int32_t extent = 0;
        int32_t buffer = 0;
        bool clip_geom = true;
        GSERIALIZED *geom_in, *geom_out;
        LWGEOM *lwgeom_in, *lwgeom_out;
        uint8_t type = 0;
 
        if (PG_ARGISNULL(0))
        {
                PG_RETURN_NULL();
        }
 
        if (PG_ARGISNULL(1))
        {
                elog(ERROR, "%s: Geometric bounds cannot be null", __func__);
                PG_RETURN_NULL();
        }
        bounds = (GBOX *)PG_GETARG_POINTER(1);
        if (bounds->xmax - bounds->xmin <= 0 || bounds->ymax - bounds->ymin <= 0)
        {
                elog(ERROR, "%s: Geometric bounds are too small", __func__);
                PG_RETURN_NULL();
        }
 
        extent = PG_ARGISNULL(2) ? 4096 : PG_GETARG_INT32(2);
        if (extent <= 0)
        {
                elog(ERROR, "%s: Extent must be greater than 0", __func__);
                PG_RETURN_NULL();
        }
 
        buffer = PG_ARGISNULL(3) ? 256 : PG_GETARG_INT32(3);
        clip_geom = PG_ARGISNULL(4) ? true : PG_GETARG_BOOL(4);
 
        geom_in = PG_GETARG_GSERIALIZED_P_COPY(0);
        type = gserialized_get_type(geom_in);
 
        /* If possible, peek into the bounding box before deserializing it to discard small geometries
         * We don't check COLLECTIONTYPE since that might be a collection of points */
        if (type == LINETYPE || type == POLYGONTYPE || type == MULTILINETYPE || type == MULTIPOLYGONTYPE)
        {
                GBOX gserialized_box;
                /* We only apply the optimization if the bounding box is available */
                if (gserialized_fast_gbox_p(geom_in, &gserialized_box) == LW_SUCCESS)
                {
                        /* Shortcut to drop geometries smaller than the resolution */
                        double geom_width = gserialized_box.xmax - gserialized_box.xmin;
                        double geom_height = gserialized_box.ymax - gserialized_box.ymin;
 
                        /* We use half of the square height and width as limit: We use this
                         * and not area so it works properly with lines */
                        double bounds_width = ((bounds->xmax - bounds->xmin) / extent) / 2.0;
                        double bounds_height = ((bounds->ymax - bounds->ymin) / extent) / 2.0;
                        if (geom_width < bounds_width && geom_height < bounds_height)
                        {
                                PG_RETURN_NULL();
                        }
                }
        }
 
        lwgeom_in = lwgeom_from_gserialized(geom_in);
 
        lwgeom_out = mvt_geom(lwgeom_in, bounds, extent, buffer, clip_geom);
        if (lwgeom_out == NULL)
                PG_RETURN_NULL();
 
        geom_out = geometry_serialize(lwgeom_out);
        lwgeom_free(lwgeom_out);
        PG_FREE_IF_COPY(geom_in, 0);
        PG_RETURN_POINTER(geom_out);
#endif
}

References buffer(), gserialized_fast_gbox_p(), gserialized_get_type(), LINETYPE, LW_SUCCESS, lwgeom_free(), lwgeom_from_gserialized(), MULTILINETYPE, MULTIPOLYGONTYPE, mvt_geom(), POLYGONTYPE, GBOX::xmax, GBOX::xmin, GBOX::ymax, and GBOX::ymin.

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