amf.public

Parameters

Name	Type	Mode
param_inputgeom	geometry	IN

Definition

DECLARE
	vexhull public.geometry;
	var_resultgeom public.geometry;
	var_inputgeom public.geometry;
	vexring public.geometry;
	cavering public.geometry;
	cavept public.geometry[];
	seglength double precision;
	var_tempgeom public.geometry;
	scale_factor float := 1;
	i integer;
	BEGIN
		-- First compute the ConvexHull of the geometry
		vexhull := public.ST_ConvexHull(param_inputgeom);
		var_inputgeom := param_inputgeom;
		--A point really has no concave hull
		IF public.ST_GeometryType(vexhull) = 'ST_Point' OR public.ST_GeometryType(vexHull) = 'ST_LineString' THEN
			RETURN vexhull;
		END IF;

-- convert the hull perimeter to a linestring so we can manipulate individual points
		vexring := CASE WHEN public.ST_GeometryType(vexhull) = 'ST_LineString' THEN vexhull ELSE public.ST_ExteriorRing(vexhull) END;
		IF abs(public.ST_X(public.ST_PointN(vexring,1))) < 1 THEN --scale the geometry to prevent stupid precision errors - not sure it works so make low for now
			scale_factor := 100;
			vexring := public.ST_Scale(vexring, scale_factor,scale_factor);
			var_inputgeom := public.ST_Scale(var_inputgeom, scale_factor, scale_factor);
			--RAISE NOTICE 'Scaling';
		END IF;
		seglength := public.ST_Length(vexring)/least(public.ST_NPoints(vexring)*2,1000) ;

vexring := public.ST_Segmentize(vexring, seglength);
		-- find the point on the original geom that is closest to each point of the convex hull and make a new linestring out of it.
		cavering := public.ST_Collect(
			ARRAY(

SELECT
					public.ST_ClosestPoint(var_inputgeom, pt ) As the_geom
					FROM (
						SELECT  public.ST_PointN(vexring, n ) As pt, n
							FROM
							generate_series(1, public.ST_NPoints(vexring) ) As n
						) As pt

)
			)
		;

var_resultgeom := public.ST_MakeLine(geom)
			FROM public.ST_Dump(cavering) As foo;

IF public.ST_IsSimple(var_resultgeom) THEN
			var_resultgeom := public.ST_MakePolygon(var_resultgeom);
			--RAISE NOTICE 'is Simple: %', var_resultgeom;
		ELSE 
			--RAISE NOTICE 'is not Simple: %', var_resultgeom;
			var_resultgeom := public.ST_ConvexHull(var_resultgeom);
		END IF;

IF scale_factor > 1 THEN -- scale the result back
			var_resultgeom := public.ST_Scale(var_resultgeom, 1/scale_factor, 1/scale_factor);
		END IF;

-- make sure result covers original (#3638)
		-- Using ST_UnaryUnion since SFCGAL doesn't replace with its own implementation
		-- and SFCGAL one chokes for some reason
		var_resultgeom := public.ST_UnaryUnion(public.ST_Collect(param_inputgeom, var_resultgeom) );
		RETURN var_resultgeom;

END;

_st_concavehull(param_inputgeom geometry)

Parameters

Definition