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SVGPath+Path.swift
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//
// SVGPath+Path.swift
// ShapeScript Lib
//
// Created by Nick Lockwood on 11/04/2022.
// Copyright © 2022 Nick Lockwood. All rights reserved.
//
import Euclid
#if canImport(SVGPath)
import SVGPath
#endif
extension Vector {
init(_ svgPoint: SVGPoint) {
self.init(svgPoint.x, svgPoint.y)
}
}
extension SVGPoint {
init(_ point: Vector) {
self.init(x: point.x, y: point.y)
}
}
extension Path {
/// Creates a path from an SVGPath
init(_ svgPath: SVGPath, detail: Int = 4, color: Color? = nil) {
self.init(subpaths: svgPath.paths(detail: detail, color: color))
}
}
extension SVGPath {
/// Creates an array of paths from an SVGPath
func paths(detail: Int = 4, color: Color? = nil) -> [Path] {
var paths = [Path]()
var points = [PathPoint]()
var startingPoint = Vector.zero
var firstCommand: SVGCommand?
var lastCommand: SVGCommand?
func endPath() {
if points.count > 1 {
if points.count > 2, points.first == points.last,
let firstCommand = firstCommand
{
updateLastPoint(nextCommand: firstCommand)
}
paths.append(Path(points))
}
points.removeAll()
firstCommand = nil
}
func updateLastPoint(nextCommand: SVGCommand) {
if points.isEmpty {
points.append(.point(startingPoint, color: color))
return
}
guard let lastElement = lastCommand else {
return
}
let p0, p1, p2: Vector, isCurved: Bool
switch nextCommand {
case .moveTo:
points[points.count - 1].isCurved = false
return
case .end:
if let firstElement = firstCommand {
updateLastPoint(nextCommand: firstElement)
}
return
case let .lineTo(point):
p2 = Vector(point)
isCurved = false
case let .quadratic(control, _), let .cubic(control, _, _):
p2 = Vector(control)
isCurved = true
case .arc:
preconditionFailure()
}
switch lastElement {
case .moveTo, .end:
return
case let .lineTo(point):
guard points.count > 1, isCurved else {
return
}
p0 = points[points.count - 2].position
p1 = Vector(point)
case let .quadratic(control, point), let .cubic(_, control, point):
p0 = Vector(control)
p1 = Vector(point)
case .arc:
preconditionFailure()
}
let d0 = (p1 - p0).normalized()
let d1 = (p2 - p1).normalized()
let isTangent = abs(d0.dot(d1)) > 0.99
points[points.count - 1].isCurved = isTangent
}
func addCommand(_ command: SVGCommand) {
switch command {
case let .moveTo(point):
endPath()
startingPoint = Vector(point)
case let .lineTo(point):
updateLastPoint(nextCommand: command)
points.append(.point(Vector(point), color: color))
case let .quadratic(p1, p2):
updateLastPoint(nextCommand: command)
guard detail > 0 else {
points.append(.curve(Vector(p1), color: color))
points.append(.point(Vector(p2), color: color))
break
}
let detail = max(detail, 2)
var t = 0.0
let step = 1 / Double(detail)
let p0 = points.last?.position ?? startingPoint
for _ in 1 ..< detail {
t += step
points.append(.curve(
quadraticBezier(p0.x, p1.x, p2.x, t),
quadraticBezier(p0.y, p1.y, p2.y, t),
color: color
))
}
points.append(.point(Vector(p2), color: color))
case let .cubic(p1, p2, p3):
updateLastPoint(nextCommand: command)
guard detail > 0 else {
points.append(.curve(Vector(p1), color: color))
points.append(.curve(Vector(p2), color: color))
points.append(.point(Vector(p3), color: color))
break
}
let detail = max(detail * 2, 3)
var t = 0.0
let step = 1 / Double(detail)
let p0 = points.last?.position ?? startingPoint
for _ in 1 ..< detail {
t += step
points.append(.curve(
cubicBezier(p0.x, p1.x, p2.x, p3.x, t),
cubicBezier(p0.y, p1.y, p2.y, p3.y, t),
color: color
))
}
points.append(.point(Vector(p3), color: color))
case let .arc(arc):
let p0 = points.last?.position ?? startingPoint
arc.asBezierPath(from: SVGPoint(p0)).forEach(addCommand)
return
case .end:
if points.last?.position != points.first?.position {
points.append(points[0])
}
startingPoint = points.first?.position ?? .zero
endPath()
}
if case .moveTo = command {} else if firstCommand == nil {
firstCommand = command
}
lastCommand = command
}
commands.forEach(addCommand)
endPath()
return paths
}
}
private func quadraticBezier(
_ p0: Double, _ p1: Double,
_ p2: Double, _ t: Double
) -> Double {
let oneMinusT = 1 - t
let c0 = oneMinusT * oneMinusT * p0
let c1 = 2 * oneMinusT * t * p1
let c2 = t * t * p2
return c0 + c1 + c2
}
private func cubicBezier(
_ p0: Double, _ p1: Double,
_ p2: Double, _ p3: Double, _ t: Double
) -> Double {
let oneMinusT = 1 - t
let oneMinusTSquared = oneMinusT * oneMinusT
let c0 = oneMinusTSquared * oneMinusT * p0
let c1 = 3 * oneMinusTSquared * t * p1
let c2 = 3 * oneMinusT * t * t * p2
let c3 = t * t * t * p3
return c0 + c1 + c2 + c3
}