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package geojson_test
import (
"fmt"
"log"
"github.com/paulmach/orb"
"github.com/paulmach/orb/geojson"
"github.com/paulmach/orb/planar"
"github.com/paulmach/orb/quadtree"
)
type CentroidPoint struct {
*geojson.Feature
}
func (cp CentroidPoint) Point() orb.Point {
// this is where you would decide how to define
// the representative point of the feature.
c, _ := planar.CentroidArea(cp.Geometry)
return c
}
func Example_centroid() {
qt := quadtree.New(orb.Bound{Min: orb.Point{0, 0}, Max: orb.Point{1, 1}})
// feature with center {0.5, 0.5} but centroid {0.25, 0.25}
f := geojson.NewFeature(orb.MultiPoint{{0, 0}, {0, 0}, {0, 0}, {1, 1}})
f.Properties["centroid"] = "0.25"
err := qt.Add(CentroidPoint{f})
if err != nil {
log.Fatalf("unexpected error: %v", err)
}
// feature with centroid {0.6, 0.6}
f = geojson.NewFeature(orb.Point{0.6, 0.6})
f.Properties["centroid"] = "0.6"
err = qt.Add(CentroidPoint{f})
if err != nil {
log.Fatalf("unexpected error: %v", err)
}
feature := qt.Find(orb.Point{0.5, 0.5}).(CentroidPoint).Feature
fmt.Printf("centroid=%s", feature.Properties["centroid"])
// Output:
// centroid=0.6
}
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