lustre_kakaomap/geojson

GeoJSON coordinate helpers for KakaoMap shapes.

Converts GeoJSON [longitude, latitude] coordinate pairs to LatLng. GeoJSON uses [lng, lat] order — this module handles the swap automatically. Pure Gleam, no FFI required.

Values

coord_pair

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pub fn coord_pair(
  lng lng: Float,
  lat lat: Float,
) -> coords.LatLng

Converts a GeoJSON [lng, lat] pair to LatLng. GeoJSON uses longitude-first order; LatLng uses latitude-first.

geojson.coord_pair(lng: 126.978, lat: 37.5665)
// -> coords.lat_lng(lat: 37.5665, lng: 126.978)

draw_line_string

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pub fn draw_line_string(
  coordinates coordinates: List(coords.LatLng),
  id id: String,
  shape_id shape_id: String,
  options extra_options: List(polyline.PolylineOption),
) -> effect.Effect(msg)

Draws GeoJSON LineString coordinates as a polyline on the map.

let coords = geojson.line_coords([#(126.978, 37.566), #(129.042, 35.114)])
geojson.draw_line_string(coords,
  id: "map", shape_id: "route",
  options: [polyline.stroke_color("#FF0000")],
)

draw_polygon_ring

</>

pub fn draw_polygon_ring(
  coordinates coordinates: List(coords.LatLng),
  id id: String,
  shape_id shape_id: String,
  options extra_options: List(polygon.PolygonOption),
) -> effect.Effect(msg)

Draws GeoJSON Polygon coordinates as a polygon on the map. The first ring is the outer boundary.

let ring = geojson.line_coords([#(127.0, 37.0), #(127.1, 37.0), #(127.05, 37.1), #(127.0, 37.0)])
geojson.draw_polygon_ring(ring,
  id: "map", shape_id: "area",
  options: [polygon.fill_color("#00FF00"), polygon.fill_opacity(0.3)],
)

line_coords

</>

pub fn line_coords(
  pairs: List(#(Float, Float)),
) -> List(coords.LatLng)

Converts a list of GeoJSON [lng, lat] tuples to a LatLng list. Useful for LineString and Polygon ring coordinates.

geojson.line_coords([#(126.978, 37.566), #(129.042, 35.114)])