respitesage / crgeojson

A GeoJSON handling library for Crystal

geojson

This shard is meant to provide a simple interface for creating, reading, and writing geoJSON strings and objects that represent them, based on the GeoJSON specification.

Installation

1. Add the dependency to your shard.yml:

dependencies:
  geojson:
    github: respitesage/crgeojson

2. Run shards install

Usage

require "geojson"

Once you've required the library, you can use the GeoJSON module to create a geometry and a feature, like so:

point = GeoJSON::Point.new longitude: -91.343, latitude: 0.018

feature = GeoJSON::Feature.new geometry: point, id: "Galapagos"

Note that this library (like the GeoJSON specification) uses positions of the form [longitude, latitude(, optional altitude/elevation)]. This is particularly important when not using named arguments to specify points and positions. Additionally, the id field above is optional. Refer to the documentation of Feature.new for more information.

Now that we have our feature, we can serialize it to GeoJSON:

feature.to_json # => %({"type": "Feature",
                #       "geometry": {"type": "Point", "coordinates": [-91.343, 0.018]},
                #       "id": "Galapagos"})

If we instead had that string and wanted to deserialize it into a feature, we could do so like this:

json_string = %({"type": "Feature",
                 "geometry": {"type": "Point", "coordinates": [-91.343, 0.018]},
                 "id": "Galapagos"})

feature = GeoJSON::Feature.from_json json_string

This library currently conforms with almost all of the GeoJSON Specification, so you can also serialize, deserialize, and programmatically manipulate FeatureCollections, MultiPoints, LineStrings, MultiLineStrings, Polygons, MultiPolygons, and GeometryCollections.

Development

Features still to be developed can be found in TODO.md. Make sure to add specs for any new features.

Contributing

1. Create a fork of this repository
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request from your branch to this repository

Contributors

• Benjamin Wade - creator and maintainer

crgeojson's Issues

Examples will not work

The examples won't work unless I use:

include GeoJSON
include GeoJSON::Coordinates

Error without this:

In lib/geojson/src/geojson/geometry/pseudo_geometry.cr:42:22

 42 | contents = CoordinateTree.new parser
                 ^-------------
Error: undefined constant CoordinateTree

The bigger problem is that the includes have to be at the top-level, and I'd rather not have it mixed into my whole environment.