point-in-polygon-hao
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1.1.0 • Public • Published

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 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)
// 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

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

Package Sidebar

Install

npm i point-in-polygon-hao

Weekly Downloads

11,347

Version

1.1.0

License

MIT

Unpacked Size

13.4 kB

Total Files

12

Last publish

Collaborators

  • rowanwins