Golang geos.Geos類代碼示例

// mergeGeometries
func mergeGeometries(g *geos.Geos, geoms []*geos.Geom, geomType string) []*geos.Geom {
	// intersections from multiple sub-polygons
	// try to merge them back to a single geometry
	if strings.HasSuffix(geomType, "Polygon") {
		polygons := flattenPolygons(g, geoms)
		polygon := g.UnionPolygons(polygons)
		if polygon == nil {
			return nil
		}
		return []*geos.Geom{polygon}
	} else if strings.HasSuffix(geomType, "LineString") {
		linestrings := flattenLineStrings(g, geoms)
		linestrings = filterInvalidLineStrings(g, linestrings)
		if len(linestrings) == 0 {
			return nil
		}
		union := g.LineMerge(linestrings)
		return union
	} else if geomType == "Point" {
		if len(geoms) >= 1 {
			return geoms[0:1]
		}
		return nil
	} else {
		panic("unexpected geometry type" + geomType)
	}
}

func Point(g *geos.Geos, node element.Node) (*geos.Geom, error) {
	geom := g.Point(node.Long, node.Lat)
	if geom == nil {
		return nil, NewGeomError("couldn't create point", 1)
	}
	g.DestroyLater(geom)
	return geom, nil
}

func destroyRings(g *geos.Geos, rings []*Ring) {
	for _, r := range rings {
		if r.geom != nil {
			g.Destroy(r.geom)
			r.geom = nil
		}
	}
}

func filterInvalidLineStrings(g *geos.Geos, geoms []*geos.Geom) []*geos.Geom {
	var result []*geos.Geom
	for _, geom := range geoms {
		if geom.Length() > 1e-9 {
			result = append(result, geom)
		} else {
			g.Destroy(geom)
		}
	}
	return result
}

func AsGeomElement(g *geos.Geos, geom *geos.Geom) (*element.Geometry, error) {
	wkb := g.AsEwkbHex(geom)
	if wkb == nil {
		return nil, errors.New("could not create wkb")
	}

	return &element.Geometry{
		Wkb:  wkb,
		Geom: geom,
	}, nil
}

func (ww *WayWriter) buildAndInsert(g *geos.Geos, w *element.Way, matches interface{}, isPolygon bool) error {
	var err error
	var geosgeom *geos.Geom
	// make copy to avoid interference with polygon/linestring matches
	way := element.Way(*w)

	if isPolygon {
		geosgeom, err = geom.Polygon(g, way.Nodes)
	} else {
		geosgeom, err = geom.LineString(g, way.Nodes)
	}
	if err != nil {
		return err
	}

	way.Geom, err = geom.AsGeomElement(g, geosgeom)
	if err != nil {
		return err
	}

	if ww.limiter != nil {
		parts, err := ww.limiter.Clip(way.Geom.Geom)
		if err != nil {
			return err
		}
		for _, p := range parts {
			way := element.Way(*w)
			way.Geom = &element.Geometry{Geom: p, Wkb: g.AsEwkbHex(p)}
			if isPolygon {
				if err := ww.inserter.InsertPolygon(way.OSMElem, matches); err != nil {
					return err
				}
			} else {
				if err := ww.inserter.InsertLineString(way.OSMElem, matches); err != nil {
					return err
				}
			}
		}
	} else {
		if isPolygon {
			if err := ww.inserter.InsertPolygon(way.OSMElem, matches); err != nil {
				return err
			}
		} else {
			if err := ww.inserter.InsertLineString(way.OSMElem, matches); err != nil {
				return err
			}
		}
	}
	return nil
}

func SplitPolygonAtGrid(g *geos.Geos, geom *geos.Geom, gridWidth, currentGridWidth float64) ([]*geos.Geom, error) {
	var result []*geos.Geom
	geomBounds := geom.Bounds()
	if geomBounds == geos.NilBounds {
		return nil, errors.New("couldn't create bounds for geom")
	}
	for _, bounds := range tileBounds(geom.Bounds(), currentGridWidth) {
		clipGeom := g.BoundsPolygon(bounds)
		if clipGeom == nil {
			return nil, errors.New("couldn't create bounds polygon")
		}
		part := g.Intersection(geom, clipGeom)
		if part == nil {
			return nil, errors.New("couldn't create intersection")
		}
		if !g.IsEmpty(part) && strings.HasSuffix(g.Type(part), "Polygon") {
			if gridWidth >= currentGridWidth {
				result = append(result, part)
			} else {
				moreParts, err := SplitPolygonAtGrid(g, part, gridWidth, currentGridWidth/10.0)
				if err != nil {
					return nil, err
				}
				result = append(result, moreParts...)
			}
		}
	}
	return result, nil
}

func Polygon(g *geos.Geos, nodes []element.Node) (*geos.Geom, error) {
	nodes = unduplicateNodes(nodes)
	if len(nodes) < 4 {
		return nil, ErrorNoRing
	}

	coordSeq, err := g.CreateCoordSeq(uint32(len(nodes)), 2)
	if err != nil {
		return nil, err
	}

	// coordSeq inherited by LinearRing, no destroy
	for i, nd := range nodes {
		err := coordSeq.SetXY(g, uint32(i), nd.Long, nd.Lat)
		if err != nil {
			return nil, err
		}
	}
	ring, err := coordSeq.AsLinearRing(g)
	if err != nil {
		// coordSeq gets Destroy by GEOS
		return nil, err
	}
	// ring inherited by Polygon, no destroy

	geom := g.Polygon(ring, nil)
	if geom == nil {
		g.Destroy(ring)
		return nil, errors.New("unable to create polygon")
	}
	g.DestroyLater(geom)
	return geom, nil
}

func geosRing(g *geos.Geos, ls lineString) (*geos.Geom, error) {
	coordSeq, err := g.CreateCoordSeq(uint32(len(ls)), 2)
	if err != nil {
		return nil, err
	}

	// coordSeq inherited by LinearRing, no destroy
	for i, p := range ls {
		err := coordSeq.SetXY(g, uint32(i), p.long, p.lat)
		if err != nil {
			return nil, err
		}
	}
	ring, err := coordSeq.AsLinearRing(g)
	if err != nil {
		// coordSeq gets Destroy by GEOS
		return nil, err
	}

	return ring, nil
}

func geosPolygon(g *geos.Geos, polygon polygon) (*geos.Geom, error) {
	if len(polygon) == 0 {
		return nil, errors.New("empty polygon")
	}

	shell, err := geosRing(g, polygon[0])
	if err != nil {
		return nil, err
	}

	holes := make([]*geos.Geom, len(polygon)-1)

	for i, ls := range polygon[1:] {
		hole, err := geosRing(g, ls)
		if err != nil {
			return nil, err
		}
		holes[i] = hole
	}

	geom := g.Polygon(shell, holes)
	if geom == nil {
		g.Destroy(shell)
		for _, hole := range holes {
			g.Destroy(hole)
		}
		return nil, errors.New("unable to create polygon")
	}
	return geom, nil
}

func LineString(g *geos.Geos, nodes []element.Node) (*geos.Geom, error) {
	nodes = unduplicateNodes(nodes)
	if len(nodes) < 2 {
		return nil, ErrorOneNodeWay
	}

	coordSeq, err := g.CreateCoordSeq(uint32(len(nodes)), 2)
	if err != nil {
		return nil, err
	}
	// coordSeq inherited by LineString
	for i, nd := range nodes {
		coordSeq.SetXY(g, uint32(i), nd.Long, nd.Lat)
	}
	geom, err := coordSeq.AsLineString(g)
	if err != nil {
		// coordSeq gets Destroy by GEOS
		return nil, err
	}
	g.DestroyLater(geom)
	return geom, nil
}

func (ww *WayWriter) buildAndInsert(geos *geos.Geos, w *element.Way, matches []mapping.Match, builder geomBuilder) {
	var err error
	// make copy to avoid interference with polygon/linestring matches
	way := element.Way(*w)
	geosgeom, err := builder(geos, way.Nodes)
	if err != nil {
		if err, ok := err.(ErrorLevel); ok {
			if err.Level() <= 0 {
				return
			}
		}
		log.Println(err)
		return
	}

	way.Geom, err = geom.AsGeomElement(geos, geosgeom)
	if err != nil {
		log.Println(err)
		return
	}

	if ww.limiter != nil {
		parts, err := ww.limiter.Clip(way.Geom.Geom)
		if err != nil {
			log.Println(err)
			return
		}
		for _, g := range parts {
			way := element.Way(*w)
			way.Geom = &element.Geometry{g, geos.AsEwkbHex(g)}
			ww.insertMatches(&way.OSMElem, matches)
		}
	} else {
		ww.insertMatches(&way.OSMElem, matches)
	}
}

func (c *Limiter) IntersectsBuffer(g *geos.Geos, x, y float64) bool {
	if c.bufferedPrep == nil {
		return true
	}
	if x < c.bufferedBbox.MinX ||
		y < c.bufferedBbox.MinY ||
		x > c.bufferedBbox.MaxX ||
		y > c.bufferedBbox.MaxY {
		return false
	}
	p := g.Point(x, y)
	if p == nil {
		return false
	}
	defer g.Destroy(p)

	c.bufferedPrepMu.Lock()
	defer c.bufferedPrepMu.Unlock()
	return g.PreparedIntersects(c.bufferedPrep, p)
}

func flattenLineStrings(g *geos.Geos, geoms []*geos.Geom) []*geos.Geom {
	var result []*geos.Geom
	for _, geom := range geoms {
		if g.Type(geom) == "MultiLineString" {
			for _, part := range g.Geoms(geom) {
				result = append(result, g.Clone(part))
			}
			g.Destroy(geom)
		} else if g.Type(geom) == "LineString" {
			result = append(result, geom)
		} else {
			log.Printf("unexpected geometry type in flattenPolygons")
			g.Destroy(geom)
		}
	}
	return result
}

func filterGeometryByType(g *geos.Geos, geom *geos.Geom, targetType string) []*geos.Geom {
	// Filter (multi)geometry for compatible `geom_type`,
	// because we can't insert points into linestring tables for example

	geomType := g.Type(geom)

	if geomType == targetType {
		// same type is fine
		return []*geos.Geom{geom}
	}
	if geomType == "Polygon" && targetType == "MultiPolygon" {
		// multipolygon mappings also support polygons
		return []*geos.Geom{geom}
	}
	if geomType == "MultiPolygon" && targetType == "Polygon" {
		// polygon mappings should also support multipolygons
		return []*geos.Geom{geom}
	}

	if g.NumGeoms(geom) >= 1 {
		// GeometryCollection or MultiLineString? return list of geometries
		var geoms []*geos.Geom
		for _, part := range g.Geoms(geom) {
			// only parts with same type
			if g.Type(part) == targetType {
				geoms = append(geoms, g.Clone(part))
			}
		}
		g.Destroy(geom)
		if len(geoms) != 0 {
			return geoms
		}
		return []*geos.Geom{}
	}
	g.Destroy(geom)
	return []*geos.Geom{}
}