PerspectiveTransform/Example/Specs/BasisVectorSpec.swift

import Quick
import Nimble
import simd
import GameKit
@testable import PerspectiveTransform

class BasisSpec: QuickSpec {
    override func spec() {
        let start = Quadrilateral(CGRect(origin: CGPoint.zero, size: CGSize(width: 152, height: 122)))
        let destination = Quadrilateral(
            CGRect(
                origin: CGPoint(x: 100, y: 100),
                size: CGSize(width: 200, height: 200)
            )
        )

        context("multiply adj by vector") {
            it("should match expected") {
                let adjM = Matrix3x3Type([-122, -152, 18544, 122, 0, 0, 0, 152, 0])
                let vector = Vector3Type([152, 122, 1])
                let result = adjM * vector
                let expected = Vector3Type([-18544, 18544, 18544])
                expect(result).to(equal(expected))
            }
        }

        context("basisVectorsToPointsMap") {
            context("any 4 points") {
                var points: [CGPoint]!
                var subject: Matrix3x3Type!

                let basisVectors = [Vector3Type(1, 0, 0),
                                    Vector3Type(0, 1, 0),
                                    Vector3Type(0, 0, 1),
                                    Vector3Type(1, 1, 1)]

                let source = GKRandomSource.sharedRandom()

                beforeEach {
                    points = source.nextFourPoints()
                    subject = Perspective(points).basisVectorsToPointsMap
                }

                it("should map base vectors to points") {
                    for (index, vector) in basisVectors.enumerated() {
                        let tranformed = subject * vector
                        expect(tranformed.dehomogenized) ≈ points[index]
                    }
                }
            }

            it("should match expected") {
                let startBasis = Matrix3x3Type([[0.0, 0.0, -1.0], [152.0, 0.0, 1.0], [0.0, 122.0, 1.0]])
                expect(Perspective(start).basisVectorsToPointsMap) ≈ (startBasis, delta:0.5)
            }

            it("should work for destination") {
                let destBasis = Matrix3x3Type([[-100.0, -100.0, -1.0], [300.0, 100.0, 1.0], [100.0, 300.0, 1.0]])
                expect(Perspective(destination).basisVectorsToPointsMap) ≈ (destBasis, delta:0.5)
            }
        }
    }
}