68 lines
2.2 KiB
PL/PgSQL
68 lines
2.2 KiB
PL/PgSQL
--
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-- Iterative densification of a set of points using Delaunay triangulation
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-- the new points have as assigned value the average value of the 3 vertex (centroid)
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--
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-- @param geomin - array of geometries (points)
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--
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-- @param colin - array of numeric values in that points
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--
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-- @param iterations - integer, number of iterations
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--
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--
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-- Returns: TABLE(geomout geometry, colout numeric)
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--
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--
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CREATE OR REPLACE FUNCTION CDB_Densify(
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IN geomin geometry[],
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IN colin numeric[],
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IN iterations integer
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)
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RETURNS TABLE(geomout geometry, colout numeric) AS $$
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DECLARE
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geotemp geometry[];
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coltemp numeric[];
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i integer;
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gs geometry[];
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g geometry;
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vertex geometry[];
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va numeric;
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vb numeric;
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vc numeric;
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center geometry;
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centerval numeric;
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tmp integer;
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BEGIN
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geotemp := geomin;
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coltemp := colin;
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FOR i IN 1..iterations
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LOOP
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-- generate TIN
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WITH a as (SELECT unnest(geotemp) AS e),
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b as (SELECT ST_DelaunayTriangles(ST_Collect(a.e),0.001, 0) AS t FROM a),
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c as (SELECT (ST_Dump(t)).geom AS v FROM b)
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SELECT array_agg(v) INTO gs FROM c;
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-- loop cells
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FOREACH g IN ARRAY gs
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LOOP
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-- append centroid
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SELECT ST_Centroid(g) INTO center;
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geotemp := array_append(geotemp, center);
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-- retrieve the value of each vertex
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WITH a AS (SELECT (ST_DumpPoints(g)).geom AS v)
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SELECT array_agg(v) INTO vertex FROM a;
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WITH a AS(SELECT unnest(geotemp) as geo, unnest(coltemp) as c)
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SELECT c INTO va FROM a WHERE ST_Equals(geo, vertex[1]);
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WITH a AS(SELECT unnest(geotemp) as geo, unnest(coltemp) as c)
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SELECT c INTO vb FROM a WHERE ST_Equals(geo, vertex[2]);
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WITH a AS(SELECT unnest(geotemp) as geo, unnest(coltemp) as c)
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SELECT c INTO vc FROM a WHERE ST_Equals(geo, vertex[3]);
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-- calc the value at the center
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centerval := (va + vb + vc) / 3;
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-- append the value
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coltemp := array_append(coltemp, centerval);
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END LOOP;
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END LOOP;
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RETURN QUERY SELECT unnest(geotemp ) as geomout, unnest(coltemp ) as colout;
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END;
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$$ language plpgsql IMMUTABLE;
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