https://github.com/rowanwins/point-in-polygon-hao
A point in polygon library based on the paper "Optimal Reliable Point-in-Polygon Test and Differential Coding Boolean Operations on Polygons" by Hao
https://github.com/rowanwins/point-in-polygon-hao
computational-geometry point-in-polygon
Last synced: 4 days ago
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A point in polygon library based on the paper "Optimal Reliable Point-in-Polygon Test and Differential Coding Boolean Operations on Polygons" by Hao
- Host: GitHub
- URL: https://github.com/rowanwins/point-in-polygon-hao
- Owner: rowanwins
- License: mit
- Created: 2019-03-22T12:04:16.000Z (about 6 years ago)
- Default Branch: master
- Last Pushed: 2024-12-22T05:56:57.000Z (5 months ago)
- Last Synced: 2025-05-11T19:48:02.890Z (8 days ago)
- Topics: computational-geometry, point-in-polygon
- Language: JavaScript
- Homepage:
- Size: 61.5 KB
- Stars: 140
- Watchers: 4
- Forks: 10
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGES.md
- Funding: FUNDING.yml
- License: LICENSE
Awesome Lists containing this project
README
A small library for detecting in a point lies inside a polygon
**Features**
- Works on polygons with holes
- Works with degenerate/self-intersecting polyons
- Returns `0` if on the edge
- Not effected by floating point errors
### Usage
Install via `npm install point-in-polygon-hao`
````
import inside from 'point-in-polygon-hao'
const polygon = [
[
[1, 1],
[1, 2],
[2, 2],
[2, 1],
[1, 1]
]
];
inside([ 1.5, 1.5 ], polygon)
// => true
inside([ 4.9, 1.2 ], polygon)
// => false
inside([1, 2], polygon)
// => 0 to indicate on edge
````
**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.
````
const polygonWithHole = [
[
[0, 0], [1, 0], [1, 1], [0, 1], [0, 0]
],
[
[0.1, 0.1], [0.1, 0.9], [0.9, 0.9], [0.9, 0.1], [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.
````
// For a point in a much larger geometry (700+ vertices)
point-in-poly-hao x 381,184 ops/sec ±0.80% (87 runs sampled)
point-in-polygon x 285,734 ops/sec ±1.33% (91 runs sampled)
robust-point-in-polygon x 267,738 ops/sec ±0.78% (93 runs sampled)
````
````
// For a point in bounding box check
point-in-poly-hao x 25,822,227 ops/sec ±2.87% (86 runs sampled)
point-in-polygon x 30,321,920 ops/sec ±2.14% (91 runs sampled)
robust-point-in-polygon x 26,708,560 ops/sec ±1.13% (91 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`~~
* Added robust-predicates to deal with some floating point errors