Tracking and altering images

At a glance

Project structure

Source bundle/
├── AlteredImageTracking/
│   ├── AppDelegate.swift
│   ├── ViewController.swift
│   ├── AlteredImage.swift
│   ├── RectangleDetector.swift
│   ├── VisualizationNode.swift
│   ├── Utilities.swift
│   ├── Base.lproj/
│   │   └── Main.storyboard
│   ├── Info.plist
│   └── Resources/
│       └── LaunchScreen.storyboard
├── AlteredImageTracking.xcodeproj/
│   ├── .xcodesamplecode.plist
│   └── project.pbxproj
└── Configuration/
    └── SampleCode.xcconfig

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 6 project/configuration file(s) and 8 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ViewController"]
    N3["ARKit APIs"]
    N1 --> N2
    N2 --> N3

Reference code

AlteredImageTracking/AppDelegate.swift:11 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions
        launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        guard ARImageTrackingConfiguration.isSupported else {
            fatalError("""
                ARKit is not available on this device. For apps that require ARKit
                for core functionality, use the `arkit` key in the key in the
                `UIRequiredDeviceCapabilities` section of the Info.plist to prevent
                the app from installing. (If the app can't be installed, this error
                can't be triggered in a production scenario.)
                In apps where AR is an additive feature, use `isSupported` to
                determine whether to show UI for launching AR experiences.
            """) // For details, see https://developer.apple.com/documentation/arkit
        }

        return true
    }
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into ARKit.

Ownership and state

classDiagram
    AppDelegate o-- UIWindow : window
    ViewController o-- ARSCNView : sceneView
    ViewController o-- UIView : messagePanel
    ViewController o-- UILabel : messageLabel

Ownership evidence

AlteredImageTracking/AppDelegate.swift:14 — stored dependency or nearest verified ownership anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    var window: UIWindow?
    // ...
}

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

Reference code

AlteredImageTracking/AlteredImage.swift:205 — representative execution boundary

        DispatchQueue.global().async { [weak self] in
            guard let self = self else { return }
            // ...
        }

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

AlteredImageTracking/AlteredImage.swift:256 — representative type boundary

protocol AlteredImageDelegate: AnyObject {
    func alteredImageLostTracking(_ alteredImage: AlteredImage)
}

The source explicitly defines local protocol relationships: AlteredImage → VisualizationNodeDelegate, ViewController → RectangleDetectorDelegate, ViewController → AlteredImageDelegate.

Access control

Reference code

AlteredImageTracking/AlteredImage.swift:18 — representative boundary

class AlteredImage {
    // ...
    private(set) var anchor: ARImageAnchor?
    // ...
}

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Naming conventions

• Types: Controller: ViewController; Delegate: AlteredImageDelegate, AppDelegate, RectangleDetectorDelegate, VisualizationNodeDelegate.
• Protocols: AlteredImageDelegate, RectangleDetectorDelegate, VisualizationNodeDelegate.
• Methods: application, viewDidLoad, viewDidAppear, searchForNewImageToTrack, runImageTrackingSession, showMessage, setMessageHidden, didTap.
• Files: AlteredImageTracking/AppDelegate.swift, AlteredImageTracking/ViewController.swift, AlteredImageTracking/AlteredImage.swift, AlteredImageTracking/RectangleDetector.swift, AlteredImageTracking/VisualizationNode.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches ARKit, UIKit, CoreML, SceneKit through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• Local protocol relationships provide an explicit substitution boundary.

Source map

• Official Apple documentation