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#![doc(html_logo_url = "https://raw.githubusercontent.com/georust/meta/master/logo/logo.png")] // Copyright 2014-2015 The GeoRust Developers // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. //! //! # Introduction //! The `geojson` crate reads and writes `GeoJSON` ([IETF RFC 7946](https://tools.ietf.org/html/rfc7946)) files, //! optionally using `serde` for serialisation. Crate users are encouraged to familiarise themselves with the spec, //! as the crate is structured around it. //! # Structure of the Crate //! GeoJSON can contain one of three top-level objects, reflected in the top-level `geojson::GeoJson` //! enum members of the same name: //! //! - [`Feature`](struct.Feature.html) //! - [`FeatureCollection`](struct.FeatureCollection.html) //! - [`Geometry`](struct.Geometry.html) //! //! With `FeatureCollection` being the most commonly used, since it can contain multiple child objects. //! A `FeatureCollection` contains `Feature` objects, each of which contains a `Geometry` object, which may be empty. //! Since the most common uses cases for GeoJSON involve the use of `Feature` and `FeatureCollection` objects, //! conversions to `Feature` are provided for both `Value` enum members and Geometry objects via the `From` trait. //! A potentially complicating factor is the `GeometryCollection` geometry type, which can contain //! one more `Geometry` objects, _including nested `GeometryCollection` objects_. //! The use of `GeometryCollection` is discouraged, however. //! //! If your primary use case for this crate is ingesting `GeoJSON` strings in order to process geometries //! using the algorithms in the [`geo`](https://docs.rs/geo) crate, you can do so by enabling the `geo-types` feature in //! your `Cargo.toml`, and using the [`quick_collection`](fn.quick_collection.html) function to //! parse [`GeoJson`](enum.GeoJson.html) objects into //! a [`geo_types::GeometryCollection`](../geo_types/struct.GeometryCollection.html). //! See [here](#conversion-to-geo-objects) for details. //! //! Conversely, if you wish to produce a `FeatureCollection` from a homogenous collection of `geo` types, a `From` impl is //! provided for `geo_types::GeometryCollection`: //! //! ```rust //! # #[cfg(feature = "geo-types")] //! // The geo-types feature is required for this functionality //! # #[cfg(feature = "geo-types")] //! use geojson::FeatureCollection; //! # #[cfg(feature = "geo-types")] //! use geo_types::{GeometryCollection, LineString, Polygon}; //! # #[cfg(feature = "geo-types")] //! use std::iter::FromIterator; //! //! # #[cfg(feature = "geo-types")] //! let poly = Polygon::new( //! LineString::from(vec![(0., 0.), (1., 1.), (1., 0.), (0., 0.)]), //! vec![], //! ); //! //! # #[cfg(feature = "geo-types")] //! let polys = vec![poly]; //! # #[cfg(feature = "geo-types")] //! let gc = GeometryCollection::from_iter(polys); //! # #[cfg(feature = "geo-types")] //! let fc = FeatureCollection::from(&gc); //! ``` //! //! This crate uses `serde` for serialization. //! To get started, add `geojson` to your `Cargo.toml`: //! //! ```text //! [dependencies] //! geojson= "*" //! ``` //! # Examples //! ## Reading //! //! ``` //! use geojson::GeoJson; //! //! let geojson_str = r#" //! { //! "type": "FeatureCollection", //! "features": [ //! { //! "type": "Feature", //! "properties": {}, //! "geometry": { //! "type": "Point", //! "coordinates": [ //! -0.13583511114120483, //! 51.5218870403801 //! ] //! } //! } //! ] //! } //! "#; //! //! let geojson = geojson_str.parse::<GeoJson>().unwrap(); //! ``` //! //! ## Writing //! //! Writing `geojson` depends on the serialization framework because some structs //! (like `Feature`) use json values for properties. //! //! ``` //! use serde_json; //! //! use serde_json::{to_value, Map}; //! //! let mut properties = Map::new(); //! properties.insert(String::from("name"), to_value("Firestone Grill").unwrap()); //! ``` //! //! `GeoJson` can then be serialized by calling `to_string`: //! //! ```rust //! use geojson::{Feature, GeoJson, Geometry, Value}; //! # fn properties() -> ::serde_json::Map<String, ::serde_json::Value> { //! # let mut properties = ::serde_json::Map::new(); //! # properties.insert( //! # String::from("name"), //! # ::serde_json::Value::String(String::from("Firestone Grill")), //! # ); //! # properties //! # } //! # fn main() { //! # let properties = properties(); //! //! let geometry = Geometry::new(Value::Point(vec![-120.66029, 35.2812])); //! //! let geojson = GeoJson::Feature(Feature { //! bbox: None, //! geometry: Some(geometry), //! id: None, //! properties: Some(properties), //! foreign_members: None, //! }); //! //! let geojson_string = geojson.to_string(); //! # } //! ``` //! //! ## Parsing //! //! GeoJSON's [spec](https://tools.ietf.org/html/rfc7946) is quite simple, but //! it has several subtleties that must be taken into account when parsing it: //! //! - The `geometry` field of a `Feature` is an `Option` //! - `GeometryCollection`s contain other `Geometry` objects, and can nest. //! //! Here's a minimal example which will parse valid GeoJSON without taking //! ownership of it. //! //! ```rust //! use geojson::{GeoJson, Geometry, Value}; //! //! /// Process top-level GeoJSON items //! fn process_geojson(gj: &GeoJson) { //! match *gj { //! GeoJson::FeatureCollection(ref ctn) => { //! for feature in &ctn.features { //! if let Some(ref geom) = feature.geometry { //! match_geometry(geom) //! } //! } //! } //! GeoJson::Feature(ref feature) => { //! if let Some(ref geom) = feature.geometry { //! match_geometry(geom) //! } //! } //! GeoJson::Geometry(ref geometry) => match_geometry(geometry), //! } //! } //! //! /// Process GeoJSON geometries //! fn match_geometry(geom: &Geometry) { //! match geom.value { //! Value::Polygon(_) => println!("Matched a Polygon"), //! Value::MultiPolygon(_) => println!("Matched a MultiPolygon"), //! Value::GeometryCollection(ref gc) => { //! println!("Matched a GeometryCollection"); //! // GeometryCollections contain other Geometry types, and can nest //! // we deal with this by recursively processing each geometry //! for geometry in gc { //! match_geometry(geometry) //! } //! } //! // Point, LineString, and their Multi– counterparts //! _ => println!("Matched some other geometry"), //! } //! } //! //! fn main() { //! let geojson_str = r#" //! { //! "type": "GeometryCollection", //! "geometries": [ //! {"type": "Point", "coordinates": [0,1]}, //! {"type": "MultiPoint", "coordinates": [[-1,0],[1,0]]}, //! {"type": "LineString", "coordinates": [[-1,-1],[1,-1]]}, //! {"type": "MultiLineString", "coordinates": [ //! [[-2,-2],[2,-2]], //! [[-3,-3],[3,-3]] //! ]}, //! {"type": "Polygon", "coordinates": [ //! [[-5,-5],[5,-5],[0,5],[-5,-5]], //! [[-4,-4],[4,-4],[0,4],[-4,-4]] //! ]}, //! { "type": "MultiPolygon", "coordinates": [[ //! [[-7,-7],[7,-7],[0,7],[-7,-7]], //! [[-6,-6],[6,-6],[0,6],[-6,-6]] //! ],[ //! [[-9,-9],[9,-9],[0,9],[-9,-9]], //! [[-8,-8],[8,-8],[0,8],[-8,-8]]] //! ]}, //! {"type": "GeometryCollection", "geometries": [ //! {"type": "Polygon", "coordinates": [ //! [[-5.5,-5.5],[5,-5],[0,5],[-5,-5]], //! [[-4,-4],[4,-4],[0,4],[-4.5,-4.5]] //! ]} //! ]} //! ] //! } //! "#; //! let geojson = geojson_str.parse::<GeoJson>().unwrap(); //! process_geojson(&geojson); //! } //! ``` //! //! ## Conversion to Geo objects //! //! The [`TryFrom`](../std/convert/trait.TryFrom.html) trait provides //! **fallible** conversions _to_ [Geo](../geo_types/index.html#structs) types from GeoJSON [`Value`](enum.Value.html) enums, //! allowing them to be measured or used in calculations. Conversely, `From` is //! implemented on the [`Value`](enum.Value.html) enum variants to allow conversion _from_ `Geo` types. //! //! **In most cases it is assumed that you want to convert GeoJSON into `geo` primitive types in order to process, transform, or measure them:** //! - `match` on `geojson`, iterating over its `features` field, yielding `Option<Feature>`. //! - process each `Feature`, accessing its `Value` field, yielding `Option<Value>`. //! //! Each [`Value`](enum.Value.html) represents a primitive type, such as a //! coordinate, point, linestring, polygon, or its multi- equivalent, **and each of these has //! an equivalent `geo` primitive type**, which you can convert to using the `std::convert::TryFrom` trait. //! //! Unifying these features, the [`quick_collection`](fn.quick_collection.html) function accepts a [`GeoJson`](enum.GeoJson.html) enum //! and processes it, producing a [`GeometryCollection`](../geo_types/struct.GeometryCollection.html) //! whose members can be transformed, measured, rotated, etc using the algorithms and functions in //! the [`geo`](https://docs.rs/geo) crate: //! //! ``` //! # #[cfg(feature = "geo-types")] //! use geojson::{quick_collection, GeoJson}; //! # #[cfg(feature = "geo-types")] //! use geo_types::GeometryCollection; //! # #[cfg(feature = "geo-types")] //! let geojson_str = r#" //! { //! "type": "FeatureCollection", //! "features": [ //! { //! "type": "Feature", //! "properties": {}, //! "geometry": { //! "type": "Point", //! "coordinates": [ //! -0.13583511114120483, //! 51.5218870403801 //! ] //! } //! } //! ] //! } //! "#; //! # #[cfg(feature = "geo-types")] //! let geojson = geojson_str.parse::<GeoJson>().unwrap(); //! // Turn the GeoJSON string into a geo_types GeometryCollection //! # #[cfg(feature = "geo-types")] //! let mut collection: GeometryCollection<f64> = quick_collection(&geojson).unwrap(); //! ``` //! //! A `Geojson` may be converted to a `geo_types::Geometry<f64>` like so: //! //! ``` //! # #[cfg(feature = "geo-types")] //! use geojson::GeoJson; //! # #[cfg(feature = "geo-types")] //! use geo_types::Geometry; //! use std::convert::TryInto; //! use std::str::FromStr; //! # #[cfg(feature = "geo-types")] //! let geojson_str = r#" //! { //! "type": "Feature", //! "properties": {}, //! "geometry": { //! "type": "Point", //! "coordinates": [ //! -0.13583511114120483, //! 51.5218870403801 //! ] //! } //! } //! "#; //! # #[cfg(feature = "geo-types")] //! let geojson = GeoJson::from_str(geojson_str).unwrap(); //! // Turn the GeoJSON string into a geo_types Geometry //! # #[cfg(feature = "geo-types")] //! let geom: geo_types::Geometry<f64> = geojson.try_into().unwrap(); //! ``` //! ### Caveats //! - Round-tripping with intermediate processing using the `geo` types may not produce identical output, //! as e.g. outer `Polygon` rings are automatically closed. //! - `geojson` attempts to output valid geometries. In particular, it may re-orient `Polygon` rings when serialising. //! //! The [`geojson_example`](https://github.com/urschrei/geojson_example) and //! [`polylabel_cmd`](https://github.com/urschrei/polylabel_cmd/blob/master/src/main.rs) crates contain example //! implementations which may be useful if you wish to perform this kind of processing yourself and require //! more granular control over performance and / or memory allocation. // only enables the `doc_cfg` feature when // the `docsrs` configuration attribute is defined #![cfg_attr(docsrs, feature(doc_cfg))] #[cfg(feature = "geo-types")] use geo_types; use serde; use serde_json; /// Bounding Boxes /// /// [GeoJSON Format Specification § 5](https://tools.ietf.org/html/rfc7946#section-5) pub type Bbox = Vec<f64>; /// Positions /// /// [GeoJSON Format Specification § 3.1.1](https://tools.ietf.org/html/rfc7946#section-3.1.1) pub type Position = Vec<f64>; pub type PointType = Position; pub type LineStringType = Vec<Position>; pub type PolygonType = Vec<Vec<Position>>; mod util; mod geojson; pub use crate::geojson::GeoJson; mod geometry; pub use crate::geometry::{Geometry, Value}; pub mod feature; mod feature_collection; pub use crate::feature_collection::FeatureCollection; pub mod errors; pub use crate::errors::Error; #[cfg(feature = "geo-types")] mod conversion; #[cfg(feature = "geo-types")] pub use conversion::quick_collection; /// Feature Objects /// /// [GeoJSON Format Specification § 3.2](https://tools.ietf.org/html/rfc7946#section-3.2) #[derive(Clone, Debug, PartialEq)] pub struct Feature { /// Bounding Box /// /// [GeoJSON Format Specification § 5](https://tools.ietf.org/html/rfc7946#section-5) pub bbox: Option<Bbox>, /// Geometry /// /// [GeoJSON Format Specification § 3.2](https://tools.ietf.org/html/rfc7946#section-3.2) pub geometry: Option<Geometry>, /// Identifier /// /// [GeoJSON Format Specification § 3.2](https://tools.ietf.org/html/rfc7946#section-3.2) pub id: Option<feature::Id>, /// Properties /// /// [GeoJSON Format Specification § 3.2](https://tools.ietf.org/html/rfc7946#section-3.2) pub properties: Option<json::JsonObject>, /// Foreign Members /// /// [GeoJSON Format Specification § 6](https://tools.ietf.org/html/rfc7946#section-6) pub foreign_members: Option<json::JsonObject>, } mod json { pub use serde::{Deserialize, Deserializer, Serialize, Serializer}; pub use serde_json::{Map, Value as JsonValue}; pub type JsonObject = Map<String, JsonValue>; }