Compute an interior point (representative point) of a geometry. Ported from the JTS Topology Suite InteriorPoint algorithm to TypeScript and Rust.
An interior point is guaranteed to lie inside the geometry (for polygons) or on the geometry (for lines/points). This is useful for label placement and point-in-polygon representative coordinates.
interior-point -f wkt -i "POLYGON ((0 0, 6 0, 6 2, 2 2, 2 8, 0 8, 0 0))"
# POINT (1 5)That L-shaped polygon is the reason the algorithm exists: its centroid is (2, 3), which lies on the boundary rather than inside it.
Each package is published on its own, carries its own README with a quick start for that language, and installs the same interior-point command.
| Package | Language | Registry |
|---|---|---|
| interior-point | TypeScript | npm |
| interior-point | Rust | crates.io |
- Polygons (2D): Scanline algorithm — picks a Y that bisects the bounding box, computes edge intersections, returns the midpoint of the longest interior interval
- Lines (1D): Vertex nearest to centroid
- Points (0D): Point nearest to centroid
- GeometryCollections: Uses the highest-dimension non-empty component
Both libraries publish the same three functions, spelled for their language, and the bundled command exposes the last two as flags.
| TypeScript | Rust | CLI | What it returns |
|---|---|---|---|
interiorPoint |
interior_point |
— | the interior point of a geometry, by the algorithm above |
verifyInteriorPoint |
verify_interior_point |
--verify |
whether a computed point lies on or in its geometry, checked through an independent point-in-polygon locator |
centroidFirstInteriorPoint |
centroid_first_interior_point |
--centroid-first |
the geometry's centroid when it lies strictly inside, and the interior point when it does not |
Verification is a check on this port's own output, not an OGC geometry validity check.
Full documentation: https://sanak.github.io/interior-point/
- CLI — installing the bundled
interior-pointcommand, its flags and its exit codes - API reference — every entry point, with the reasoning behind each: TypeScript, Rust
This project was developed with the assistance of Claude Code. Every ported member carries a @jts anchor naming its upstream counterpart, and the ported test suites run against JTS's own test resources, so the result is verifiable against the original Java sources rather than taken on trust.
This project contains algorithms ported from JTS, licensed under EPL 2.0 / EDL 1.0.