geojson_to_mbtiles.go

package geojsonreader

import (
    "encoding/json"
    "fmt"
    "github.com/murphy214/mercantile"
    "github.com/paulmach/orb"
    gj2 "github.com/paulmach/orb/geojson"
)

type Tile struct {
    Tile  mercantile.TileID
    Lat   float64
    Lon   float64
    Index int
}

// TilesFromGeoJSON converts GeoJSON Polygon(s) to MBTiles
func TilesFromGeoJSON(gjBytes []byte, zoomLevel int) ([]Tile, error) {
    fc := gj2.NewFeatureCollection()
    if err := json.Unmarshal(gjBytes, fc); err != nil {
        return nil, fmt.Errorf("error decoding GeoJSON: %v", err)
    }

    var tiles []Tile

    var tilesAdded int

    for _, feature := range fc.Features {
        bound := feature.Geometry.Bound()
      
        topLeftLon, topLeftLat := bound.LeftTop().Lon(), bound.LeftTop().Lat()
        bottomRightLon, bottomRightLat := bound.RightBottom().Lon(), bound.RightBottom().Lat()

        topLeftTile := mercantile.Tile(topLeftLon, topLeftLat, zoomLevel)
        bottomRightTile := mercantile.Tile(bottomRightLon, bottomRightLat, zoomLevel)

        for x := topLeftTile.X; x <= bottomRightTile.X; x++ {
            for y := bottomRightTile.Y; y >= topLeftTile.Y; y-- {
                tileID := mercantile.TileID{X: x, Y: y, Z: uint64(zoomLevel)}
                center := mercantile.Center(tileID)

                if bound.Contains(orb.Point{center[0], center[1]}) {
                    tiles = append(tiles, Tile{
                        Tile:  tileID,
                        Lon:   center[0],
                        Lat:   center[1],
                        Index: tilesAdded,
                    })
                    tilesAdded++
                }
            }
        }
    }

    return tiles, nil
}