Clipper2 — Java Port

A Java port of Clipper2, the polygon clipping and offsetting library by Angus Johnson.

Original C# library: https://github.com/AngusJohnson/Clipper2 License: Boost Software License 1.0

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What is Clipper2?

Clipper2 performs boolean polygon clipping (intersection, union, difference, xor) and polygon offsetting on 2D polygons. It handles complex cases including self-intersecting polygons, holes, and open paths. This Java port provides the same functionality under the same Boost license.

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Features

• Boolean clipping: Intersection, Union, Difference, Xor
• Polygon offsetting with Miter, Round, and Square join types
• Open path offsetting with Butt, Round, and Square end caps
• Rectangle clipping (rectClip, rectClipLines)
• Path simplification (simplifyPath, ramerDouglasPeucker, trimCollinear)
• Minkowski Sum and Difference
• Polygon triangulation
• Both integer (Path64) and floating-point (PathD) coordinate types
• PolyTree output for hierarchical hole/outer polygon relationships

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Requirements

• Java 17 or later
• Gradle (tested with 9.4.0)

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Build & Test

gradle test

All 50 unit tests should pass.

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Project Structure

clipper2-java/
├── src/
│   ├── main/java/clipper2/
│   │   ├── Clipper.java                  # Static convenience facade
│   │   ├── core/                         # Point64, PointD, Path64, Rect64, etc.
│   │   ├── engine/                       # ClipperBase, Clipper64, ClipperD, PolyTree, ...
│   │   ├── offset/                       # ClipperOffset, JoinType, EndType
│   │   ├── rectclip/                     # RectClip64, RectClipLines64
│   │   ├── minkowski/                    # Minkowski sum/difference
│   │   └── triangulation/               # Triangulation
│   └── test/java/clipper2/
│       ├── TestPolygons.java
│       ├── TestLines.java
│       ├── TestPolytree.java
│       ├── TestOffset.java
│       ├── TestRectClip.java
│       ├── TestMinkowski.java
│       ├── TestSimplify.java
│       └── utils/ClipperFileIO.java
└── Tests/                                # Shared test data (*.txt)

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Quick Example

import clipper2.Clipper;
import clipper2.core.*;
import clipper2.engine.*;

// Create subject and clip polygons
Paths64 subj = new Paths64();
subj.add(Clipper.makePath(new long[]{0, 0, 100, 0, 100, 100, 0, 100}));

Paths64 clip = new Paths64();
clip.add(Clipper.makePath(new long[]{50, 50, 150, 50, 150, 150, 50, 150}));

// Intersect
Paths64 solution = Clipper.intersect(subj, clip, FillRule.NonZero);

// Offset (expand by 10 units)
Paths64 inflated = Clipper.inflatePaths(subj, 10,
    clipper2.offset.JoinType.Miter,
    clipper2.offset.EndType.Polygon);

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Differences from the C# Version

• Field names use Java conventions: x/y instead of X/Y on Point64/PointD
• No USINGZ (z-callback) support
• ReuseableDataContainer64 is a top-level public class (in clipper2.engine)

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License

Boost Software License 1.0 — same as the original Clipper2 library.