func SymmetricDifference(js geojson.GeoJSON) (*geojson.FeatureCollection, error) {
polygons, err := geometryToPolygonList(js)
if err != nil {
return nil, err
}
var features []geojson.Feature
for i := 0; i < len(polygons); i++ {
a := polygons[i]
for j := 0; j < len(polygons); j++ {
if i == j {
continue
}
var c s2.Polygon
b := polygons[j]
c.InitToDifference(a, b)
a = &c
}
if a.NumLoops() > 0 {
feat := geojson.Feature{
Typ: "Feature",
Geometry: s2PolygonToGeometry(*a),
}
features = append(features, feat)
}
}
fc := &geojson.FeatureCollection{
Typ: "FeatureCollection",
Features: features,
}
return fc, nil
}
func Difference(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.InitToDifference(a, b)
a = &c
}
return featureCollectionFromS2Polygon(a), nil
}