geojson-slicer

slice a given set of geojson features to fit within a certain bounding box

Installation

Use standard npm installation

npm install --save geojson-slicer

Usage

require the geojson-slicer function and call it with the required parameters

const slicer = require('geojson-slicer'),
    geoJsonObject = {
        type : 'FeatureCollection',
        features : [ ... ]
    },
    bounds = [0, 1, 2, 3];  // compare geobound-object inputs

let group = slicer(geoJsonObject, bounds, {
        cutFeatures : false
    }),
    cut = slicer(geoJsonObject, bounds);

// group and cut describe GeoJSON-FeatureCollections with the same features.
// group contains the original features provided in geoJsonObject
// cut contains the features cutted at the borders of the given bounds

Parameters

The slicer method accepts three parameters:

• Feature(s) (required)
• bounds (requried)
• Options (optional)

Feature(s) (required)

This property describes the input of features. There are three different ways to pass features:

Pass a list of features

[{
    type : 'Feature',
    geometry : {
        type : 'Point',
        coordinates : [ ... ]
    },
    properties : { ... }
},{
    type : 'Feature',
    geometry : {
        type : 'LineString',
        coordinates : [ ... ]
    },
    properties : { ... }
}]

Pass a FeatureCollection

{
    type : 'FeatureCollection',
    features : [{
        type : 'Feature',
        geometry : {
            type : 'Point',
            coordinates : [ ... ]
        },
        properties : { ... }
    },{
        type : 'Feature',
        geometry : {
            type : 'LineString',
            coordinates : [ ... ]
        },
        properties : { ... }
    }]
}

Pass a single feature

{
    type : 'Feature',
    geometry : {
        type : 'LineString',
        coordinates : [ ... ]
    },
    properties : { ... }
}

Please note that the last way is only useful if you want to cut the privided feature by the borders.

bounds (requried)

Bounds the features should be sliced with. The format of the bounds need to be a valid input for a WGS84 bound object constructor call.

Options (optional)

You can pass additional options to control the behavior.

cutFeatures (default: true)

Cut Features to fit within bounds. If set to false, the complete feature is added instead of a part of the feature that lies within the given bounds.

filter (default: null)

Optional filter function to prevent a feature to be added to the sliced boundary. Input parameter of the passed function is the feature.

A boolean return value is expected:

• true: apply a boundary check and add the feature if it lies within the boundary,
• false: do not add this feature to the given bound, although it may lie within the boundary.

Passing no function applies the boundary check for each feature (same behavior than passing a function that returns true all the time).

Future Work

The following improvements are planned:

• add tests
• support Polygon with wholes
• support MultiPoint, MultiLineString, MultiPolygon and GeometryCollection

Contribute

Feel free to add issues or pull requests. I'm glad for every kind of feedback!