bezier_kit

bezier_kit

bezier_kit is a comprehensive Bezier Path library written in Dart.

About

bezier_kit has been manually converted from the original BezierKit in Swift. It's based on the fork of BezierKit ref 11a87c26 from June 28 of 2022 (version 0.15.0).

Features

  • x Constructs linear (line segment), quadratic, and cubic Bézier curves
  • x Determines positions, derivatives, and normals along curves
  • x Lengths of curves via Legendre-Gauss quadrature
  • x Intersects curves and computes cubic curve self-intersection to any degree of accuracy
  • x Determines bounding boxes, extrema,
  • x Locates nearest on-curve location to point
  • x to any degree of accuracy
  • x Splits curves into subcurves
  • x Offsets and outlines curves
  • Comprehensive Unit and Integration Test Coverage
  • Complete Documentation

Installation

Dart

dart pub add dart_lapack

Flutter

flutter pub add dart_lapack

Usage

Constructing & Drawing Curves

bezier_kit supports cubic Bezier curves (CubicCurve) and quadratic Bezier curves (QuadraticCurve) as well as line segments (LineSegment) each of which adopts the BezierCurve protocol that encompasses most API functionality.

import 'package:bezier_kit/bezier_kit.dart';

final curve = CubicCurve(
  p0: Point(x: 100, y: 25),
  p1: Point(x: 10, y: 90),
  p2: Point(x: 110, y: 100),
  p3: Point(x: 150, y: 195),
);

final canvas: Canvas = ...        // your graphics context here
final draw = Draw(canvas);
draw.drawSkeleton(curve: curve);  // draws visual representation of curve control points
draw.drawCurve(curve: curve);     // draws the curve itself

Intersecting Curves

The intersections(with curve: BezierCurve) -> [Intersection] method determines each intersection between self and curve as an array of Intersection objects. Each intersection has two fields: t1 represents the t-value for self at the intersection while t2 represents the t-value for curve at the intersection. You can use the ponit(at:) method on either of the curves to calculate the coordinates of the intersection by passing in the corresponding t-value for the curve.

Cubic curves may self-intersect which can be determined by calling the selfIntersections() method.

final intersections = curve1.intersectionsWithCurve(curve2);
final points = intersections.map((i) => curve1.point(at: i.t1));

draw.drawCurve(curve: curve1);
draw.drawCurve(curve: curve2);
for (final p in points) {
  draw.drawPoint(origin: p);
}

Splitting Curves

The split(from:, to:) method produces a subcurve over a given range of t-values. The split(at:) method can be used to produce a left subcurve and right subcurve created by splitting across a single t-value.

draw.setColor(color: Draw.lightGrey);
draw.drawSkeleton(curve: curve);
draw.drawCurve(curve: curve);
final subcurve = curve.split(from: 0.25, to: 0.75); // or try (leftCurve, rightCurve) = curve.split(at:)
draw.setColor(color: Draw.red);
draw.drawCurve(curve: subcurve);
draw.drawCircle(center: curve.point(at: 0.25), radius: 3);
draw.drawCircle(center: curve.point(at: 0.75), radius: 3);

Determining Bounding Boxes

final boundingBox = curve.boundingBox;
draw.drawSkeleton(context, curve: curve);
draw.drawCurve(context, curve: curve);
draw.setColor(context, color: Draw.pinkish);
draw.drawBoundingBox(context, boundingBox: curve.boundingBox);

More

bezier_kit is a powerful library with a lot of functionality. For the time being the best way to see what it offers is to build the example Flutter app and check out each of the provided demos.

Testing

bezier_kit includes the entire test suite from the original sources converted from Swift to Dart.

To run the test suite do:

dart test

License

bezier_kit is released under the MIT license. See LICENSE for details.

Libraries

bezier_kit