GeoZero

Zero-Copy reading and writing of geospatial data.

GeoZero defines an API for reading geospatial data formats without an intermediate representation. It defines traits which can be implemented to read and convert to an arbitrary format or render geometries directly.

Supported geometry types:

• OGC Simple Features
• Circular arcs as defined by SQL-MM Part 3
• TIN

Supported dimensions: X, Y, Z, M, T

Available implementations

Applications

• flatgeobuf-gpu: Demo rendering FlatGeobuf to GPU
• flatgeobuf-bevy: Demo rendering FlatGeobuf with WebGPU (native platforms) and WebGL2 (Web/WASM)
• flatgeobuf-wasm: WASM demo displaying FlatGeobuf as SVG

Conversion API

Convert a GeoJSON polygon to geo-types and calculate centroid:

let geojson = GeoJson(r#"{"type": "Polygon", "coordinates": [[[0, 0], [10, 0], [10, 6], [0, 6], [0, 0]]]}"#);
if let Ok(Geometry::Polygon(poly)) = geojson.to_geo() {
    assert_eq!(poly.centroid().unwrap(), Point::new(5.0, 3.0));
}

Full source code: geo_types.rs

Convert GeoJSON to a GEOS prepared geometry:

let geojson = GeoJson(r#"{"type": "Polygon", "coordinates": [[[0, 0], [10, 0], [10, 6], [0, 6], [0, 0]]]}"#);
let geom = geojson.to_geos().expect("GEOS conversion failed");
let prepared_geom = geom.to_prepared_geom().expect("to_prepared_geom failed");
let geom2 = geos::Geometry::new_from_wkt("POINT (2.5 2.5)").expect("Invalid geometry");
assert_eq!(prepared_geom.contains(&geom2), Ok(true));

Full source code: geos.rs

Read FlatGeobuf subset as GeoJSON:

let mut file = BufReader::new(File::open("countries.fgb")?);
let mut fgb = FgbReader::open(&mut file)?.select_bbox(8.8, 47.2, 9.5, 55.3)?;
println!("{}", fgb.to_json()?);

Full source code: geojson.rs

Read FlatGeobuf data as geo-types geometries and calculate label position with polylabel-rs:

let mut file = BufReader::new(File::open("countries.fgb")?);
let mut fgb = FgbReader::open(&mut file)?.select_all()?;
while let Some(feature) = fgb.next()? {
    let name: String = feature.property("name").unwrap();
    if let Ok(Geometry::MultiPolygon(mpoly)) = feature.to_geo() {
        if let Some(poly) = &mpoly.0.iter().next() {
            let label_pos = polylabel(&poly, &0.10).unwrap();
            println!("{name}: {label_pos:?}");
        }
    }
}

Full source code: polylabel.rs

PostGIS usage examples

Select and insert geo-types geometries with rust-postgres. Requires the with-postgis-postgres feature:

let mut client = Client::connect(&std::env::var("DATABASE_URL").unwrap(), NoTls)?;

let row = client.query_one(
    "SELECT 'SRID=4326;POLYGON ((0 0, 2 0, 2 2, 0 2, 0 0))'::geometry",
    &[],
)?;

let value: wkb::Decode<geo_types::Geometry<f64>> = row.get(0);
if let Some(geo_types::Geometry::Polygon(poly)) = value.geometry {
    assert_eq!(
        *poly.exterior(),
        vec![(0.0, 0.0), (2.0, 0.0), (2.0, 2.0), (0.0, 2.0), (0.0, 0.0)].into()
    );
}

// Insert geometry
let geom: geo_types::Geometry<f64> = geo::Point::new(1.0, 3.0).into();
let _ = client.execute(
    "INSERT INTO point2d (datetimefield,geom) VALUES(now(),ST_SetSRID($1,4326))",
    &[&wkb::Encode(geom)],
);

Select and insert geo-types geometries with SQLx. Requires the with-postgis-sqlx feature:

let pool = PgPoolOptions::new()
    .max_connections(5)
    .connect(&env::var("DATABASE_URL").unwrap())
    .await?;

let row: (wkb::Decode<geo_types::Geometry<f64>>,) =
    sqlx::query_as("SELECT 'SRID=4326;POLYGON ((0 0, 2 0, 2 2, 0 2, 0 0))'::geometry")
        .fetch_one(&pool)
        .await?;
let value = row.0;
if let Some(geo_types::Geometry::Polygon(poly)) = value.geometry {
    assert_eq!(
        *poly.exterior(),
        vec![(0.0, 0.0), (2.0, 0.0), (2.0, 2.0), (0.0, 2.0), (0.0, 0.0)].into()
    );
}

// Insert geometry
let geom: geo_types::Geometry<f64> = geo::Point::new(10.0, 20.0).into();
let _ = sqlx::query(
    "INSERT INTO point2d (datetimefield,geom) VALUES(now(),ST_SetSRID($1,4326))",
)
.bind(wkb::Encode(geom))
.execute(&pool)
.await?;

Using compile-time verification requires type overrides:

let _ = sqlx::query!(
    "INSERT INTO point2d (datetimefield, geom) VALUES(now(), $1::geometry)",
    wkb::Encode(geom) as _
)
.execute(&pool)
.await?;

struct PointRec {
    pub geom: wkb::Decode<geo_types::Geometry<f64>>,
    pub datetimefield: Option<OffsetDateTime>,
}
let rec = sqlx::query_as!(
    PointRec,
    r#"SELECT datetimefield, geom as "geom!: _" FROM point2d"#
)
.fetch_one(&pool)
.await?;
assert_eq!(
    rec.geom.geometry.unwrap(),
    geo::Point::new(10.0, 20.0).into()
);

Full source code: postgis.rs

Processing API

Count vertices of an input geometry:

struct VertexCounter(u64);

impl GeomProcessor for VertexCounter {
    fn xy(&mut self, _x: f64, _y: f64, _idx: usize) -> Result<()> {
        self.0 += 1;
        Ok(())
    }
}

let mut vertex_counter = VertexCounter(0);
geometry.process(&mut vertex_counter, GeometryType::MultiPolygon)?;

Full source code: geozero-api.rs

Find maximal height in 3D polygons:

struct MaxHeightFinder(f64);

impl GeomProcessor for MaxHeightFinder {
    fn coordinate(&mut self, _x: f64, _y: f64, z: Option<f64>, _m: Option<f64>, _t: Option<f64>, _tm: Option<u64>, _idx: usize) -> Result<()> {
        if let Some(z) = z {
            if z > self.0 {
                self.0 = z
            }
        }
        Ok(())
    }
}

let mut max_finder = MaxHeightFinder(0.0);
while let Some(feature) = fgb.next()? {
    let geometry = feature.geometry().unwrap();
    geometry.process(&mut max_finder, GeometryType::MultiPolygon)?;
}

Full source code: geozero-api.rs

Render polygons:

struct PathDrawer<'a> {
    canvas: &'a mut CanvasRenderingContext2D,
    path: Path2D,
}

impl<'a> GeomProcessor for PathDrawer<'a> {
    fn xy(&mut self, x: f64, y: f64, idx: usize) -> Result<()> {
        if idx == 0 {
            self.path.move_to(vec2f(x, y));
        } else {
            self.path.line_to(vec2f(x, y));
        }
        Ok(())
    }
    fn linestring_end(&mut self, _tagged: bool, _idx: usize) -> Result<()> {
        self.path.close_path();
        self.canvas.fill_path(
            mem::replace(&mut self.path, Path2D::new()),
            FillRule::Winding,
        );
        Ok(())
    }
}

Full source code: flatgeobuf-gpu

Read a FlatGeobuf dataset with async HTTP client applying a bbox filter and convert to GeoJSON:

let url = "https://flatgeobuf.org/test/data/countries.fgb";
let mut fgb = HttpFgbReader::open(url)
    .await?
    .select_bbox(8.8, 47.2, 9.5, 55.3)
    .await?;

let mut fout = BufWriter::new(File::create("countries.json")?);
let mut json = GeoJsonWriter::new(&mut fout);
fgb.process_features(&mut json).await?;

Full source code: geojson.rs

Create a KD-tree index with kdbush:

struct PointIndex {
    pos: usize,
    index: KDBush,
}

impl geozero::GeomProcessor for PointIndex {
    fn xy(&mut self, x: f64, y: f64, _idx: usize) -> Result<()> {
        self.index.add_point(self.pos, x, y);
        self.pos += 1;
        Ok(())
    }
}

let mut points = PointIndex {
    pos: 0,
    index: KDBush::new(1249, DEFAULT_NODE_SIZE),
};
read_geojson_geom(&mut f, &mut points)?;
points.index.build_index();

Full source code: kdbush.rs