# turf_pip 0.0.2

A small library for detecting if a point lies inside a polygon




## Installing
```
export PUB_HOSTED_URL=https://pub.mirror.p-hatan.com
flutter pub add 'turf_pip:0.0.2'
```
Published: 2024-01-31T11:01:46.515872Z
Expected archive SHA-256: ba4fd414baffd5d7b30880658ad6db82461c49ec023f8ffd0c23d398ad8b14be

Available in cache; verification: upstream_checksum
## Direct dependencies
- turf: ^0.0.8

## Package README (untrusted upstream documentation)
# turf_pip

A small library for detecting if a point lies inside a polygon.

A port of: [point-in-polygon-hao NPM package](https://www.npmjs.com/package/point-in-polygon-hao).

Point in polygon library based on the paper "Optimal Reliable Point-in-Polygon Test and Differential Coding Boolean Operations on Polygons" by Hao.



## Features

- Works on polygons with holes
- Works with degenerate/self-intersecting polyons
- Returns `PointInPolygonResult.isOnEdge` if on the edge, `PointInPolygonResult.isOutside` if inside and `PointInPolygonResult.isOutside` if outside
- Not effected by floating point errors

### Usage

Install via `dart pub add turf_pip`

```dart
import 'package:turf_pip/turf_pip.dart';

const polygon = Polygon(coordinates:[
  [
    Position.of([1, 1]),
    Position.of([1, 2]),
    Position.of([2, 2]),
    Position.of([2, 1]),
    Position.of([1, 1])
  ]
]);

pointInPolygon(Point(coordinates: Position.of([ 1.5, 1.5 ]), polygon)
// => PointInPolygonResult.isInside

pointInPolygon(Point(coordinates: Position.of([ 4.9, 1.2 ]), polygon)
// => PointInPolygonResult.isOutside

pointInPolygon(Point(coordinates: Position.of([1, 2]), polygon)
// => PointInPolygonResult.isOnEdge
```

**Note:** The input polygon format aligns with the GeoJson specification for polygons. This means that the first and last coordinate in a polygon must be repeated, if not this library will throw an error.

```dart
var polygonWithHole = Polygon(coordinates:([
  [
    Position.of([0, 0]),
    Position.of([1, 0]),
    Position.of([1, 1]),
    Position.of([0, 1]),
    Position.of([0, 0]),
  ],
  [
    Position.of([0.1, 0.1]),
    Position.of([0.1, 0.9]),
    Position.of([0.9, 0.9]),
    Position.of([0.9, 0.1]),
    Position.of([0.1, 0.1]),
  ]
]);
```

The library does not support multi-polygons.

### Comparisons

Some rough comparisons to similar libraries.
While `point-in-polygon` is slightly faster in most cases it does not support polygons with holes or degenerate polygons.

```text
// For a point in a much larger geometry (700+ vertices)
point-in-poly-hao x 474,180 ops/sec ±0.55% (93 runs sampled)
point-in-polygon x 489,649 ops/sec ±0.75% (91 runs sampled)
robust-point-in-polygon x 376,268 ops/sec ±0.79% (89 runs sampled)
```

```text
// For a point in bounding box check
point-in-poly-hao x 29,365,704 ops/sec ±1.30% (90 runs sampled)
point-in-polygon x 42,339,450 ops/sec ±0.78% (95 runs sampled)
robust-point-in-polygon x 20,675,569 ops/sec ±0.65% (95 runs sampled)
```

### Algorithm

This library is based on the paper [Optimal Reliable Point-in-Polygon Test and
Differential Coding Boolean Operations on Polygons](https://www.researchgate.net/publication/328261365_Optimal_Reliable_Point-in-Polygon_Test_and_Differential_Coding_Boolean_Operations_on_Polygons)

### Other notes

- Works irrespective of winding order of polygon
- Does not appear to be effected by floating point errors compared to `point-in-polygon` or `robust-point-in-polygon`

## Changelog
## 0.0.2

- This is solely a quality release, without new functionality.

## 0.0.1

- Initial version.