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 follows the structure and functionality of Clipper2's C# implementation, with method names adapted to JavaScript conventions. Where C# uses PascalCase for methods (AddPath, Execute), this port uses camelCase (addPath, execute). Class names remain unchanged

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