# geozero

**Repository Path**: paulwang007/geozero

## Basic Information

- **Project Name**: geozero
- **Description**: https://github.com/georust/geozero.git
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-10-10
- **Last Updated**: 2021-10-10

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# GeoZero

[![CI build](https://github.com/georust/geozero/workflows/CI-Linux/badge.svg)](https://github.com/georust/geozero/actions)
[![crates.io version](https://img.shields.io/crates/v/geozero.svg)](https://crates.io/crates/geozero)
[![docs.rs docs](https://docs.rs/geozero/badge.svg)](https://docs.rs/geozero)
[![Discord Chat](https://img.shields.io/discord/598002550221963289.svg)](https://discord.gg/Fp2aape)

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](https://en.wikipedia.org/wiki/Simple_Features)
* Circular arcs as defined by SQL-MM Part 3
* TIN

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

## Available implementations

* GeoJSON Reader + Writer
* [GEOS](https://github.com/georust/geos) Reader + Writer
* [GDAL](https://github.com/georust/gdal) geometry Reader + Writer
* WKB Reader + Writer supporting
  - PostGIS geometries for [rust-postgres](https://github.com/sfackler/rust-postgres) and [SQLx](https://github.com/launchbadge/sqlx)
  - GeoPackage geometries for [SQLx](https://github.com/launchbadge/sqlx)
* WKT Writer
* SVG Writer
* [geo-types](https://github.com/georust/geo) Reader + Writer

[geozero-shp](https://github.com/georust/geozero/tree/master/geozero-shp) [![crates.io version](https://img.shields.io/crates/v/geozero-shp.svg)](https://crates.io/crates/geozero-shp)
[![docs.rs docs](https://docs.rs/geozero-shp/badge.svg)](https://docs.rs/geozero-shp)

* Shapefile Reader

[flatgeobuf](https://github.com/flatgeobuf/flatgeobuf) [![crates.io version](https://img.shields.io/crates/v/flatgeobuf.svg)](https://crates.io/crates/flatgeobuf)
[![docs.rs docs](https://docs.rs/flatgeobuf/badge.svg)](https://docs.rs/flatgeobuf)

* FlatGeobuf Reader

## Applications

* [flatgeobuf-gpu](https://github.com/pka/flatgeobuf-gpu): Demo rendering FlatGeobuf to GPU
* [flatgeobuf-bevy](https://github.com/pka/flatgeobuf-bevy): Demo rendering FlatGeobuf with WebGPU (native platforms) and WebGL2 (Web/WASM)
* [flatgeobuf-wasm](https://github.com/pka/flatgeobuf-wasm): WASM demo displaying FlatGeobuf as SVG


## Conversion API

Convert a GeoJSON polygon to geo-types and calculate centroid:
```rust
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](./geozero/tests/geo_types.rs)


Convert GeoJSON to a [GEOS](https://github.com/georust/geos) prepared geometry:
```rust
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](./geozero/tests/geos.rs)


Read FlatGeobuf subset as GeoJSON:
```rust
let mut file = BufReader::new(File::open("countries.fgb")?);
let mut fgb = FgbReader::open(&mut file)?;
fgb.select_bbox(8.8, 47.2, 9.5, 55.3)?;
println!("{}", fgb.to_json()?);
```
Full source code: [geojson.rs](./geozero/tests/geojson.rs)


Read FlatGeobuf data as geo-types geometries and calculate label position with [polylabel-rs](https://github.com/urschrei/polylabel-rs):
```rust
let mut file = BufReader::new(File::open("countries.fgb")?);
let mut fgb = FgbReader::open(&mut file)?;
fgb.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](./geozero/tests/polylabel.rs)


## PostGIS usage examples

Select and insert geo-types geometries with rust-postgres:
```rust
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:
```rust
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](https://docs.rs/sqlx/0.5.1/sqlx/macro.query.html?search=insert#force-a-differentcustom-type): 
```rust
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](./geozero/tests/postgis.rs)


## Processing API

Count vertices of an input geometry:
```rust
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](./geozero/tests/geozero-api.rs)

Find maximal height in 3D polygons:
```rust
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](./geozero/tests/geozero-api.rs)

Render polygons:
```rust
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](https://github.com/pka/flatgeobuf-gpu)

Read a FlatGeobuf dataset with async HTTP client applying a bbox filter and convert to GeoJSON:
```rust
let url = "https://flatgeobuf.org/test/data/countries.fgb";
let mut fgb = HttpFgbReader::open(url).await?;
fgb.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](./geozero/tests/geojson.rs)


Create a KD-tree index with [kdbush](https://github.com/pka/rust-kdbush):
```rust
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](./geozero/tests/kdbush.rs)