pgrouting/sql/alpha_shape/alpha_shape.sql at master · gisdevelope/pgrouting · GitHub

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/*PGR-GNU*****************************************************************

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*/

-----------------------------------------------------------------------

-- Core function for alpha shape computation.

-- The sql should return vertex ids and x,y values. Return ordered

-- vertex ids.

-----------------------------------------------------------------------

CREATE OR REPLACE FUNCTION pgr_alphashape(sql text, alpha float8 DEFAULT 0, OUT x float8, OUT y float8)

RETURNS SETOF record

AS '${MODULE_PATHNAME}', 'alphashape'

LANGUAGE c VOLATILE;

----------------------------------------------------------

-- Draws an alpha shape around given set of points.

-- ** This should be rewritten as an aggregate. **

----------------------------------------------------------

CREATE OR REPLACE FUNCTION pgr_pointsAsPolygon(query varchar, alpha float8 DEFAULT 0)

RETURNS geometry AS

DECLARE

r record;

geoms geometry[];

vertex_result record;

i int;

n int;

spos int;

q text;

x float8[];

y float8[];

BEGIN

geoms := array[]::geometry[];

i := 1;

FOR vertex_result IN EXECUTE 'SELECT x, y FROM pgr_alphashape('''|| query || ''', ' || alpha || ')'

LOOP

x[i] = vertex_result.x;

y[i] = vertex_result.y;

i := i+1;

END LOOP;

n := i;

IF n = 1 THEN

RAISE NOTICE 'n = 1';

RETURN NULL;

END IF;

spos := 1;

q := 'SELECT ST_GeometryFromText(''POLYGON((';

FOR i IN 1..n LOOP

IF x[i] IS NULL AND y[i] IS NULL THEN

q := q || ', ' || x[spos] || ' ' || y[spos] || '))'',0) AS geom;';

EXECUTE q INTO r;

geoms := geoms || array[r.geom];

q := '';

ELSE

IF q = '' THEN

spos := i;

q := 'SELECT ST_GeometryFromText(''POLYGON((';

END IF;

IF i = spos THEN

q := q || x[spos] || ' ' || y[spos];

ELSE

q := q || ', ' || x[i] || ' ' || y[i];

END IF;

END LOOP;

RETURN ST_BuildArea(ST_Collect(geoms));

END;

LANGUAGE 'plpgsql' VOLATILE STRICT;

pgrouting/sql/alpha_shape/alpha_shape.sql at master · gisdevelope/pgrouting · GitHub

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