geo-polyline-tools/README.md

A javaScript library that provides utility functions to encode and decode polyline coordinates

# Geo Polyline Tools

## Description

`geo-polyline-tools` is a lightweight JavaScript library that provides utility functions to encode and decode polyline coordinates, based on Google's Encoded Polyline Algorithm. It also supports converting between GeoJSON LineString features and polyline strings.

## Features
- **Encode**: Convert an array of latitude and longitude coordinates into a polyline string.
- **Decode**: Convert a polyline string back into an array of latitude and longitude coordinates.
- **GeoJSON Support**: Encode and decode GeoJSON LineString features to and from polyline strings.
- **Precision Control**: Specify the precision of the coordinates during encoding and decoding.

## Installation

To install the package via npm, run the following command:
```bash
npm install geo-polyline-tools
```
Or via yarn:
```bash
yarn add geo-polyline-tools
```

## Usage
Here’s how to use the geo-polyline-tools package in your project:

### Importing the Library
You can import the library into your project using ES modules or CommonJS:

**ES Module**
```js
import polyline from 'geo-polyline-tools';
```

**CommonJS**
```js
const polyline = require('geo-polyline-tools');
```

### Encoding Coordinates
To encode an array of coordinates into a polyline string:
```js
const coords = [[38.5, -120.2], [40.7, -120.95], [43.252, -126.453]];
const encoded = polyline.encode(coords, 5);
console.log(encoded); // Example output: '_p~iF~ps|U_ulLnnqC_mqNvxq`@'
```

### Decoding a Polyline String
To decode a polyline string back into an array of coordinates:
```js
const str = '_p~iF~ps|U_ulLnnqC_mqNvxq`@';
const decoded = polyline.decode(str, 5);
console.log(decoded); // Example output: [[38.5, -120.2], [40.7, -120.95], [43.252, -126.453]]
```

### Working with GeoJSON
#### From GeoJSON to Polyline
To convert a GeoJSON LineString to a polyline string:
```js
const geojson = {
  type: 'Feature',
  geometry: {
    type: 'LineString',
    coordinates: [[38.5, -120.2], [40.7, -120.95], [43.252, -126.453]],
  },
};

const encoded = polyline.fromGeoJSON(geojson, 5);
console.log(encoded); // Example output: '_p~iF~ps|U_ulLnnqC_mqNvxq`@'
```

#### From Polyline to GeoJSON
To convert a polyline string back to a GeoJSON LineString:
```js
const str = '_p~iF~ps|U_ulLnnqC_mqNvxq`@';
const geojson = polyline.toGeoJSON(str, 5);
console.log(geojson);
/*
Example output:
{
  type: 'LineString',
  coordinates: [[38.5, -120.2], [40.7, -120.95], [43.252, -126.453]],
}
*/
```

## License
This library is licensed under the MIT License. See the [LICENSE](https://www.npmjs.com/package/LICENSE) file for details.

## Support
For any issues or questions, please contact [support@barikoi.com](mailto:support@barikoi.com).

<img src="https://docs.barikoi.com/img/barikoi-logo-black.svg" height="30" />