Rotate Points

RotatePoints.swift

public static func rotate(points: [StrokePoint], byRadians radians: Double) -> [StrokePoint] {
	let centroid = StrokePoint.centroid(points)
	let cosvalue = cos(radians)
	let sinvalue = sin(radians)
	var newPoints: [StrokePoint] = []
	for point in points {
		let qx = (point.x - centroid.x) * cosvalue - (point.y - centroid.y) * sinvalue + centroid.x
		let qy = (point.x - centroid.x) * sinvalue + (point.y - centroid.y) * cosvalue + centroid.y
		newPoints.append(StrokePoint(x: qx, y: qy))
	}
	return newPoints
}