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    mapxus-polygon-clipping

    0.12.3 • Public • Published

    polygon-clipping

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

    npm version build status test coverage

    Quickstart

    const polygonClipping = require('polygon-clipping')
     
    const poly1 = [[[0,0],[2,0],[0,2],[0,0]]]
    const poly2 = [[[-1,0],[1,0],[0,1],[-1,0]]]
     
    polygonClipping.union       (poly1, poly2 /* , poly3, ... */)
    polygonClipping.intersection(poly1, poly2 /* , poly3, ... */)
    polygonClipping.xor         (poly1, poly2 /* , poly3, ... */)
    polygonClipping.difference  (poly1, poly2 /* , poly3, ... */)

    API

    /* All functions take one or more [multi]polygon(s) as input */
     
    polygonClipping.union       (<geom>, ...<geoms>)
    polygonClipping.intersection(<geom>, ...<geoms>)
    polygonClipping.xor         (<geom>, ...<geoms>)
     
    /* The clipGeoms will be subtracted from the subjectGeom */
    polygonClipping.difference(<subjectGeom>, ...<clipGeoms>)

    Input

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

    • MultiPolygons may contain touching or overlapping Polygons.
    • rings are not required to be self-closing.
    • rings may contain repeated points, which are ignored.
    • rings may be self-touching and/or self-crossing. Self-crossing rings will be interpreted using the even-odd rule.
    • winding order of rings does not matter.
    • inner rings may extend outside their outer ring. The portion of inner rings outside their outer ring is dropped.
    • inner rings may touch or overlap each other.

    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:

    • outer rings will be wound counter-clockwise, and inner rings clockwise.
    • inner rings will not extend outside their outer ring.
    • rings will not overlap, nor share an edge with each other.
    • rings will be self-closing.
    • rings will not contain repeated points.
    • rings will not contain superfluous points (intermediate points along a straight line).
    • rings will not be self-touching nor self-crossing.
    • rings may touch each other, but may not cross each other.

    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.

    Changelog

    This project adheres to Semantic Versioning.

    The full changelog is available at CHANGELOG.md.

    Authors

    Sponsors

    Please contact Mike Fogel if you or your company is interested in sponsoring work on specific bug fixes or feature requests.

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    Install

    npm i mapxus-polygon-clipping

    DownloadsWeekly Downloads

    0

    Version

    0.12.3

    License

    MIT

    Unpacked Size

    361 kB

    Total Files

    9

    Last publish

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