PolylineKit.Core 0.1.0-alpha.1

PolylineKit.Core

.NET methods for numeric area and region overlap, with no external runtime dependencies. Includes self-intersecting paths with explicit fill rules, plus normalization, transforms, resampling and alignment. Targets .NET Standard 2.0 and .NET 10. MIT licensed.

Install the alpha candidate

Version 0.1.0-alpha.1 is prepared for evaluation. Until publication on NuGet.org, use the verified local feed produced by the package verification guide:

dotnet add MyApp/MyApp.csproj package PolylineKit.Core --version 0.1.0-alpha.1 --source /absolute/path/to/feed

Measure zone coverage

using PolylineKit;

Point2[] zone = [new(0, 0), new(6, 0), new(6, 2),
                new(2, 2), new(2, 6), new(0, 6)];
Point2[] footprint = [new(1, 1), new(5, 1), new(5, 5), new(1, 5)];
const PathFillRule rule = PathFillRule.NonZero;

double zoneArea = PolylineArea.FilledArea(zone, rule); // 20; cache for this zone
double coveredArea = PolylineArea.IntersectionArea(zone, footprint, rule); // 7
double? coverage = zoneArea > 0 ? coveredArea / zoneArea : null; // 0.35
var overlap = PolylineArea.CompareRegions(zone, footprint, rule);
// FirstArea = 20; SecondArea = 16; UnionArea = 29; IoU = 7/29.

The example uses C# 12 collection expressions. Older compilers can use explicit new Point2[] { new Point2(...), ... } arrays. Paths close implicitly; NonZero and EvenOdd fill rules are supported. An undefined coverage ratio is represented by null, not zero. Summing overlapping footprints' individual coverage can double-count their shared area.

Contracts and limits

Each PolylineArea operand is one ordered walk, with at least three retained vertices. Null, empty, too-short and nonfinite inputs throw; valid collinear walks may have zero area. Coordinates are planar, and areas use squared coordinate units. Input is not quantized, projected, normalized or resampled implicitly. Calculations use double; tiny features near large coordinates can lose precision.

For holes and disconnected components in the current source, use PreparedRegion.FromRings and RegionArea. Preparation copies coordinates without inferring holes or reversing rings. Empty collections are valid; every supplied ring still needs three retained vertices. The current alpha candidate includes these APIs; earlier locally built candidates predate them. Use the verified package pair.

Use CompareRegions for union, XOR, IoU and Jaccard distance; BetweenGraphs for the integral of absolute vertical separation between increasing-x graphs. Normalization and alignment are separate operations. For a trusted simple ring alone, a shoelace sum is cheaper than general fill-aware processing.

See the area guide, transformations, and performance and memory. The assembly retains its PolylineKit.Winding name for binary compatibility; all public types use the PolylineKit namespace. The core never references Clipper2. For resolved contours or decimal-grid comparisons, use the optional PolylineKit.Clipper adapter.