func Union(js geojson.GeoJSON) (*geojson.FeatureCollection, error) {
polygons, err := geometryToPolygonList(js)
if err != nil {
return nil, err
}
a := polygons[0]
for i := 1; i < len(polygons); i++ {
var c s2.Polygon
b := polygons[i]
c.InitToUnion(a, b)
a = &c
}
return featureCollectionFromS2Polygon(a), nil
}
func Intersection(js geojson.GeoJSON) (*geojson.FeatureCollection, error) {
polygons, err := geometryToPolygonList(js)
if err != nil {
return nil, err
}
var intersections []*s2.Polygon
for i := 0; i < len(polygons); i++ {
a := polygons[i]
for j := i + 1; j < len(polygons); j++ {
var c s2.Polygon
b := polygons[j]
c.InitToIntersection(a, b)
intersections = append(intersections, &c)
}
}
a := intersections[0]
for i := 1; i < len(intersections); i++ {
b := intersections[i]
var c s2.Polygon
c.InitToUnion(a, b)
a = &c
}
return featureCollectionFromS2Polygon(a), nil
}
