clipper2-ts

TypeScript port of Angus Johnson's Clipper2 library for polygon clipping and offsetting

Installation

npm install @countertype/clipper2-ts

Usage

import { Clipper, FillRule, JoinType, EndType } from '@countertype/clipper2-ts';

// Define polygons as arrays of points
const subject = [[
  { x: 0, y: 0 },
  { x: 100, y: 0 },
  { x: 100, y: 100 },
  { x: 0, y: 100 }
]];

const clip = [[
  { x: 50, y: 50 },
  { x: 150, y: 50 },
  { x: 150, y: 150 },
  { x: 50, y: 150 }
]];

// Boolean operations
const intersection = Clipper.intersect(subject, clip, FillRule.NonZero);
const union = Clipper.union(subject, clip, FillRule.NonZero);
const difference = Clipper.difference(subject, clip, FillRule.NonZero);
const xor = Clipper.xor(subject, clip, FillRule.NonZero);

// Polygon offsetting (inflate/deflate)
const offset = Clipper.inflatePaths(subject, 10, JoinType.Round, EndType.Polygon);

API

This port maintains API compatibility with Clipper2's C# implementation. Key types:

• Point64 - Integer coordinates {x: number, y: number}
• Path64 - Array of Point64
• Paths64 - Array of Path64
• FillRule - EvenOdd, NonZero, Positive, Negative
• ClipType - Intersection, Union, Difference, Xor

For detailed API documentation, see the official Clipper2 docs

Testing

The port includes 235 tests validating against Clipper2's reference test suite:

npm test              # Run all 235 tests
npm test:coverage     # Run with coverage report

Test results: 194/195 polygon tests pass (99.5%), matching C# reference implementation exactly. The single failure (Test 16, bow-tie polygon) also fails in C#

License

Boost Software License 1.0 (same as Clipper2)

Credits

Original library by Angus Johnson. TypeScript port by Jeremy Tribby