BezierKit

To integrate BezierKit into your Xcode project using CocoaPods, add the following to your Podfile target:

target '<Your Target Name>' do
    pod 'BezierKit', '>= 0.16.5'
end

Then, run pod install in your terminal.

Add BezierKit as a dependency in your Package.swift file by adding its URL to the dependencies array.

// swift-tools-version:5.0
import PackageDescription

let package = Package(
    name: "<Your Target Name>",
    dependencies: [
        .package(url: "https://github.com/hfutrell/BezierKit.git", from: "0.16.5"),
    ]
)

BezierKit provides CubicCurve, QuadraticCurve, and LineSegment types. All these types conform to the BezierCurve protocol. You can use the Draw utility to render them via CoreGraphics.

• Draw.drawSkeleton(context, curve): Draws a visual representation of the curve's control points.
• Draw.drawCurve(context, curve): Draws the actual curve.

import BezierKit

let curve = CubicCurve(
    p0: CGPoint(x: 100, y: 25),
    p1: CGPoint(x: 10, y: 90),
    p2: CGPoint(x: 110, y: 100),
    p3: CGPoint(x: 150, y: 195)
 )
 
 let context: CGContext = ...       // your graphics context here
 Draw.drawSkeleton(context, curve)  // draws visual representation of curve control points
 Draw.drawCurve(context, curve)     // draws the curve itself

You can extract portions of a curve using two methods:

• split(from:to:): Returns a single subcurve representing the range between two t-values.
• split(at:): Returns a tuple (leftCurve, rightCurve) split at a specific t-value.

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

Use the intersections(with:) method on a BezierCurve to find where it intersects another curve. This returns an array of Intersection objects.

Each Intersection object contains:

• t1: The t-value on the original curve (self).
• t2: The t-value on the passed curve.

You can resolve these t-values into CGPoint coordinates using the point(at:) method.

For cubic curves, you can also use selfIntersections() to find where a curve intersects itself.

let intersections: [Intersection] = curve1.intersections(with: curve2)
let points: [CGPoint] = intersections.map { curve1.point(at: $0.t1) }

Draw.drawCurve(context, curve: curve1)
Draw.drawCurve(context, curve: curve2)
for p in points {
    Draw.drawPoint(context, origin: p)
}

Every BezierCurve has a boundingBox property that returns the rectangular area containing the curve. You can visualize this using Draw.drawBoundingBox(context, boundingBox:).

let 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)