[postgis-users] Get points from a MULTILINESTRING

[TECHER David]

Hi Tyler

The following code is a simple example in PL/PGSQL, not in C

I hope it could help you for trying to writting your code in C ;)

The PLP/PGSQL code is as the end of my message

Example

testgis=# SELECT * FROM points_from_linetype('MULTILINESTRING((0 0,1 1,1 
2),(2 3,3 2,5 4))'::geometry);
 idx_geom | idx_point | point_x | point_y
----------+-----------+---------+---------
        1 |         1 |       0 |       0
        1 |         2 |       1 |       1
        1 |         3 |       1 |       2
        2 |         1 |       2 |       3
        2 |         2 |       3 |       2
        2 |         3 |       5 |       4
(6 lignes)

testgis=# SELECT * FROM points_from_linetype('LINESTRING(2 3,3 2,5 
4)'::geometry);
 idx_geom | idx_point | point_x | point_y
----------+-----------+---------+---------
        1 |         1 |       2 |       3
        1 |         2 |       3 |       2
        1 |         3 |       5 |       4
(3 lignes)

Here is the code..You can improve it I think :)


DROP TYPE PointSetFromLinetype CASCADE;

CREATE TYPE PointSetFromLinetype AS (idx_geom int4,idx_point  
int4,point_x double precision, point_y double precision);


CREATE OR REPLACE FUNCTION points_from_linetype(geometry) RETURNS SETOF 
PointSetFromLinetype AS $$ 
DECLARE
geom ALIAS FOR $1;
Idx_Geom int4 :=1;
Num_Geom int4 :=0;
Nb_Points_In_Ring int4;
Idx_Point int4 := 1;
j PointSetFromLinetype;
BEGIN
/*
    Get the number of points
*/
SELECT INTO Num_Geom NumGeometries(multi(geom))+1 ;
/* Parsing the Geometry */
WHILE Idx_Geom < Num_Geom
     LOOP
         SELECT INTO Nb_Points_In_Ring 
npoints(GeometryN(multi(geom),Idx_Geom))+1;
          WHILE Idx_Point < Nb_Points_In_Ring
          LOOP
             SELECT INTO j 
Idx_Geom,Idx_Point,x(pointn(GeometryN(multi(geom),Idx_Geom),Idx_Point)),y(pointn(GeometryN(multi(geom),Idx_Geom),Idx_Point));
             RETURN NEXT  j;
                  Idx_Point := Idx_Point + 1;
          END LOOP; -- End - FOR 1
          Idx_Point := 1;
          Idx_Geom := Idx_Geom + 1;
     END  LOOP; -- End - while
END;
$$ LANGUAGE plpgsql stable;

--david;
http://www.davidgis.fr


Tyler Durden a écrit :
> Hi,
> I'm new to postgis and I'm trying to build a extension in C that
> receives a MULTILINESTRING  geom and I need to get all points
> contained.
>
> Any ideas?
>
> Thanks i advance,
> Tyler
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> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>


	

	
		
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