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geom.go
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geom.go
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package osm
import (
"fmt"
"math"
"github.com/ctessum/geom"
"github.com/ctessum/geom/op"
"github.com/paulmach/osm"
)
// GeomTags holds a geometry object and the tags that apply to it.
type GeomTags struct {
geom.Geom
Tags map[string][]string
}
func tagsToMap(tags osm.Tags) map[string][]string {
if len(tags) == 0 {
return nil
}
o := make(map[string][]string)
for _, t := range tags {
o[t.Key] = append(o[t.Key], t.Value)
}
return o
}
// Geom converts the OSM data to geometry objects, keeping the tag information.
func (o *Data) Geom() ([]*GeomTags, error) {
items := make([]*GeomTags, 0, len(o.Ways))
for _, r := range o.Relations {
if _, ok := o.dependentRelations[r.ID]; !ok {
if r != nil {
g, err := relationToGeom(r, o.Relations, o.Ways, o.Nodes, make(map[osm.RelationID]struct{}))
if err != nil {
return nil, err
}
items = append(items, &GeomTags{
Geom: g,
Tags: tagsToMap(r.Tags),
})
}
}
}
for _, w := range o.Ways {
if _, ok := o.dependentWays[w.ID]; !ok {
if w != nil && len(w.Nodes) > 0 {
items = append(items, &GeomTags{
Geom: wayToGeom(w, o.Nodes),
Tags: tagsToMap(w.Tags),
})
}
}
}
for _, n := range o.Nodes {
if _, ok := o.dependentNodes[n.ID]; !ok {
p, ok := nodeToPoint(n)
if ok {
items = append(items, &GeomTags{
Geom: p,
Tags: tagsToMap(n.Tags),
})
}
}
}
return items, nil
}
func nodeToPoint(n *Node) (geom.Point, bool) {
if n == nil {
return geom.Point{X: math.NaN(), Y: math.NaN()}, false
}
return geom.Point{X: n.Lon, Y: n.Lat}, true
}
func wayToGeom(way *Way, nodes map[osm.NodeID]*Node) geom.Geom {
if wayIsClosed(way) {
return wayToPolygon(way, nodes)
}
return wayToLineString(way, nodes)
}
// wayIsClosed determines whether a way represents a polygon.
func wayIsClosed(way *Way) bool {
return way.Nodes[0] == way.Nodes[len(way.Nodes)-1]
}
// wayToPolygon converts a way to a polygon
func wayToPolygon(way *Way, nodes map[osm.NodeID]*Node) geom.Polygon {
p := make(geom.Polygon, 1)
for _, n := range way.Nodes {
point, ok := nodeToPoint(nodes[n])
if ok {
p[0] = append(p[0], point)
}
}
return p
}
// wayToLineString converts a way to a LineString
func wayToLineString(way *Way, nodes map[osm.NodeID]*Node) geom.LineString {
var p geom.LineString
for _, n := range way.Nodes {
point, ok := nodeToPoint(nodes[n])
if ok {
p = append(p, point)
}
}
return p
}
// relationToGeom converts a relation to a geometry object.
func relationToGeom(relation *Relation,
relations map[osm.RelationID]*Relation, ways map[osm.WayID]*Way,
nodes map[osm.NodeID]*Node, idStack map[osm.RelationID]struct{}) (geom.Geom, error) {
var nNodes, nLines, nPolygons int
for _, m := range relation.Members {
switch m.Type {
case osm.TypeWay:
if w, ok := ways[osm.WayID(m.Ref)]; ok && len(w.Nodes) > 0 && wayIsClosed(w) {
nPolygons++
} else {
nLines++
}
case osm.TypeNode:
nNodes++
}
}
if nPolygons == len(relation.Members) {
return relationToPolygon(relation, ways, nodes)
}
if nLines == len(relation.Members) {
return relationToMultiLineString(relation, ways, nodes), nil
}
if nNodes == len(relation.Members) {
return relationToMultiPoint(relation, nodes), nil
}
return relationToGeometryCollection(relation, relations, ways, nodes, idStack)
}
// relationToMultiPoint converts a relation to a MultiPoint
func relationToMultiPoint(relation *Relation,
nodes map[osm.NodeID]*Node) geom.MultiPoint {
p := make(geom.MultiPoint, 0, len(relation.Members))
for _, m := range relation.Members {
switch m.Type {
case osm.TypeNode:
point, ok := nodeToPoint(nodes[osm.NodeID(m.Ref)])
if ok {
p = append(p, point)
}
default:
panic(fmt.Errorf("unsupported relation type %T", m.Type))
}
}
return p
}
// relationToPolygon converts a relation to a polygon
func relationToPolygon(relation *Relation, ways map[osm.WayID]*Way,
nodes map[osm.NodeID]*Node) (geom.Polygon, error) {
var p geom.Polygon
for _, m := range relation.Members {
switch m.Type {
case osm.TypeWay:
if w := ways[osm.WayID(m.Ref)]; w != nil {
p = append(p, wayToPolygon(w, nodes)[0])
}
default:
panic(fmt.Errorf("unsupported relation type %T", m.Type))
}
}
if err := op.FixOrientation(p); err != nil {
return nil, err
}
return p, nil
}
// relationToMultiLineString converts a relation to a MultiLineString,
// deleting its contained elements from 'ways' and 'nodes'.
func relationToMultiLineString(relation *Relation, ways map[osm.WayID]*Way,
nodes map[osm.NodeID]*Node) geom.MultiLineString {
var p geom.MultiLineString
for _, m := range relation.Members {
switch m.Type {
case osm.TypeWay:
if w := ways[osm.WayID(m.Ref)]; w != nil {
p = append(p, wayToLineString(w, nodes))
}
default:
panic(fmt.Errorf("unsupported relation type %T", m.Type))
}
}
return p
}
func relationToGeometryCollection(relation *Relation,
relations map[osm.RelationID]*Relation, ways map[osm.WayID]*Way,
nodes map[osm.NodeID]*Node, idStack map[osm.RelationID]struct{}) (geom.Geom, error) {
p := make(geom.GeometryCollection, 0, len(relation.Members))
for _, m := range relation.Members {
switch m.Type {
case osm.TypeWay:
way := ways[osm.WayID(m.Ref)]
if way != nil && len(way.Nodes) > 0 {
p = append(p, wayToGeom(way, nodes))
}
case osm.TypeNode:
point, ok := nodeToPoint(nodes[osm.NodeID(m.Ref)])
if ok {
p = append(p, point)
}
case osm.TypeRelation:
id := osm.RelationID(m.Ref)
if _, ok := idStack[id]; ok {
continue // Skip self-references, which cause infinite recursion.
}
idStack[id] = struct{}{}
if r := relations[id]; r != nil {
g, err := relationToGeom(r, relations, ways, nodes, idStack)
if err != nil {
return nil, err
}
p = append(p, g)
}
default:
panic(fmt.Errorf("unsupported relation type %T", m.Type))
}
}
return p, nil
}
// GeomType specifies the valid geometry types.
type GeomType int
const (
// Point is a point geometry.
Point GeomType = iota
// Line is a linear geometry.
Line
// Poly is a polygonal geometry.
Poly
)
func countGeomTagsTypes(gt []*GeomTags) (points, lines, polys int, err error) {
for _, g := range gt {
pt, l, pl, err := countGeometryTypes(g.Geom)
if err != nil {
return -1, -1, -1, err
}
points += pt
lines += l
polys += pl
}
return
}
func countGeometryTypes(g geom.Geom) (points, lines, polys int, err error) {
switch g.(type) {
case geom.Point:
points++
case geom.MultiPoint:
points++
case geom.LineString, geom.MultiLineString:
lines++
case geom.Polygon:
polys++
case geom.GeometryCollection:
for _, f := range g.(geom.GeometryCollection) {
pt, l, pl, err := countGeometryTypes(f)
if err != nil {
return -1, -1, -1, err
}
points += pt
lines += l
polys += pl
}
default:
return -1, -1, -1, fmt.Errorf("invalid geometry type %T", g)
}
return
}
// DominantType returns the most frequently occurring type among the
// given features.
func DominantType(gt []*GeomTags) (GeomType, error) {
points, lines, polys, err := countGeomTagsTypes(gt)
if err != nil {
return -1, err
}
if points >= lines && points >= polys {
return Point, nil
}
if lines > points && lines >= polys {
return Line, nil
}
if polys > points && polys > lines {
return Poly, nil
}
panic(fmt.Errorf("no dominant type: %d, %d, %d", points, lines, polys))
}