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/*PGR-GNU*****************************************************************
Copyright (c) 2018 Celia Virginia Vergara Castillo
Mail: project@pgrouting.org
------
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
********************************************************************PGR-GNU*/
--------------
--------------
-- alpha_shape
--------------
--------------
--v3.0
CREATE FUNCTION pgr_alphaShape(
geometry, -- geometry
alpha FLOAT DEFAULT 0
)
RETURNS geometry AS
$BODY$
DECLARE
geom geometry;
delauny_query TEXT;
BEGIN
delauny_query = format($$
WITH
original AS (
SELECT %1$L::geometry AS geom
),
delauny AS (
SELECT (ST_Dump(ST_DelaunayTriangles(geom, 0 , 0))).*
FROM original
),
delauny_info AS (
SELECT delauny.path[1] AS id,
(ST_DumpPoints(delauny.geom)).path[2] as seq,
(ST_DumpPoints(delauny.geom)).geom
FROM delauny
)
SELECT
id,
seq AS source,
-1 AS target,
1 AS cost,
ST_X(geom)::FLOAT AS x1,
ST_Y(geom)::FLOAT AS y1,
0::FLOAT AS x2,
0::FLOAT AS y2
FROM delauny_info WHERE seq != 4;
$$, $1);
--RAISE NOTICE '%', delauny_query;
-- RETURN;
WITH a AS (SELECT 'GEOMETRYCOLLECTION(' || string_agg(textgeom,',') || ')' as geome
FROM _pgr_alphaShape(delauny_query, $2))
SELECT ST_GeomFromText(geome) FROM a
INTO geom;
RETURN geom;
END
$BODY$
LANGUAGE plpgsql VOLATILE STRICT
COST 100;
COMMENT ON FUNCTION pgr_alphashape(geometry, FLOAT)
IS 'pgr_alphaShape
- Parameters
- An SQL with columns: geom
- Optional Parameters
- alpha := 0
- Documentation:
- ${PROJECT_DOC_LINK}/pgr_alphaShape.html
';
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