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Centroids!

This application reads a valid geojson FeatureCollection and returns a valid geojson FeatureColleciton of centroids.

In the output:

  • All properties are retained.
  • Polygon features become points that represent the Polygon's centroid.
  • LineString features become points that represent the middle of the LineString.
  • Point features do not change.
  • I have no idea how this handles MultiPolygons.

This is a Flask application that uses the Shapely Python library by @sgillies. Issues and pull requests welcome!

The service can be accessed in two ways: an upload/download page and a web service.

Upload/download

The upload/download page can be found here. It is pretty self explanatory.

Web service

The web service lives at http://centroids.herokuapp.com/centroids. You can post to it with geojson.

Here is an example of how you might do that from the command line with curl (example from @invisiblefunnel):

$ curl -X POST -H "Content-Type: application/json" -d \
 '{
   "type": "FeatureCollection",
   "features": [
     {
       "type": "Feature",
       "properties": {},
       "geometry": {
         "type": "Polygon",
         "coordinates": [
           [
             [
               -80.93490600585938,
               35.263561862152095
             ],
             [
               -80.69320678710938,
               35.32745068492882
             ],
             [
               -80.60531616210938,
               35.14124815600257
             ],
             [
               -80.83328247070312,
               35.06597313798418
             ],
             [
               -80.93490600585938,
               35.263561862152095
             ]
           ]
         ]
       }
     }
   ]
 }' http://centroids.herokuapp.com/centroids

Should return:

{
  "features": [
    {
      "geometry": {
        "coordinates": [
          -80.76829071683488, 
          35.199632857787904
        ], 
        "type": "Point"
      }, 
      "properties": {}, 
      "type": "Feature"
    }
  ], 
  "type": "FeatureCollection"
}

Running locally

Optionally create a virtual environment

virtualenv venv
source venv/bin/activate

Install requirements

pip install -r requirements.txt

Start the server

python hello.py

You should now be able to visit the application at http://127.0.0.1:5000/.

Notes

To run on Heroku requires a third party BUILDPACK for Heroku