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polyclip-ts

Apply boolean polygon clipping operations (intersection, union, difference, xor) to your Polygons & MultiPolygons.

Installing

If you use npm, npm install polyclip-ts. You can also download the latest release on GitHub. For vanilla HTML in modern browsers, import polyclip-ts from Skypack:

<script type="module">
import * as polyclip from "https://cdn.skypack.dev/polyclip-ts";

polyclip.intersection(…)
</script>

For legacy environments, you can load polyclip-ts’s UMD bundle from an npm-based CDN such as jsDelivr; a polyclip global is exported:

<script src="https://cdn.jsdelivr.net/npm/polyclip-ts/dist/polyclip-ts.umd.min.js"></script>
<script>
polyclip.intersection(…)
</script>

Quickstart

<!-- prettier-ignore-start -->
import * as polyclip from "polyclip-ts"

const poly1 = [[[0,0],[2,0],[0,2],[0,0]]]
const poly2 = [[[-1,0],[1,0],[0,1],[-1,0]]]

polyclip.union       (poly1, poly2 /* , poly3, ... */)
polyclip.intersection(poly1, poly2 /* , poly3, ... */)
polyclip.xor         (poly1, poly2 /* , poly3, ... */)
polyclip.difference  (poly1, poly2 /* , poly3, ... */)
<!-- prettier-ignore-end -->

API

/* All functions take one or more [multi]polygon(s) as input */

polyclip.union       (geom, ...moreGeoms)
polyclip.intersection(geom, ...moreGeoms)
polyclip.xor         (geom, ...moreGeoms)

/* The moreGeoms will be subtracted from the geom */
polyclip.difference  (geom, ...moreGeoms)

Input

Each positional argument (geom) may be either a Polygon or a MultiPolygon. The GeoJSON spec is followed, with the following notes/modifications:

Output

For non-empty results, output will always be a MultiPolygon containing one or more non-overlapping, non-edge-sharing Polygons. The GeoJSON spec is followed, with the following notes/modifications:

In the event that the result of the operation is the empty set, output will be a MultiPolygon with no Polygons: [].

Correctness

Run: npm test

The tests are broken up into unit tests and end-to-end tests. The end-to-end tests are organized as GeoJSON files, to make them easy to visualize thanks to GitHub's helpful rendering of GeoJSON files. Browse those tests here.

Performance

The Martinez-Rueda-Feito polygon clipping algorithm is used to compute the result in O((n+k)*log(n)) time, where n is the total number of edges in all polygons involved and k is the number of intersections between edges.

Authors

Based on