Sample CodeiOS, iPadOS, Mac CatalystReviewed 2026-07-21View on Apple Developer

Applying visual effects to foreground subjects

At a glance

Item Summary
Purpose Segment the foreground subjects of an image and composite them to a new background with visual effects.
App architecture A Swift sample with the source-visible chain SubjectLiftingEffectsAppContentViewEffectsPipelineSwiftUI / CoreImage APIs.
Main patterns SwiftUI environment injection, Binding-based state propagation, Publisher-backed observable state
Project style 3 scanned source file(s) across Swift, organized around ranked entry, type, and file boundaries.
Execution model Source-visible boundaries: DispatchQueue.main.async, DispatchQueue(label:); none alone proves a background thread.
State/event model Source-visible mechanisms: SwiftUI state property wrapper, ObservableObject, @Published.
Key frameworks/packages SwiftUI, Combine, CoreImage, Foundation, PhotosUI; these are source dependencies, not architecture labels.

Project structure

Source bundle/
├── SubjectLiftingEffects/
│   ├── SubjectLiftingEffectsApp.swift
│   ├── ContentView.swift
│   └── EffectsPipeline.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── SubjectLiftingEffects.xcodeproj/
    ├── .xcodesamplecode.plist
    └── project.pbxproj

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 3 project/configuration file(s) and 10 source declaration(s).

Overall architecture

Reference code

SubjectLiftingEffects/SubjectLiftingEffectsApp.swift:11 — architecture anchor

@main
struct SubjectLiftingEffectsApp: App {

    /// A pipeline to define as an environment object.
    @StateObject private var pipeline = EffectsPipeline()

    /// A scene for the app's main window group.
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(pipeline)
        }
    }
}

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 Vision.

Ownership and state

Ownership evidence

SubjectLiftingEffects/SubjectLiftingEffectsApp.swift:15 — stored dependency or nearest verified ownership anchor

@main
struct SubjectLiftingEffectsApp: App {
    // ...
    @StateObject private var pipeline = EffectsPipeline()
    // ...
}
Owner Object or state Relationship Mutation authority
SubjectLiftingEffectsApp EffectsPipeline (pipeline) owns wrapper-managed state Owning lexical scope
EffectPicker Effect (effect) borrows mutable state The upstream binding owner is authoritative
BackgroundPicker Background (background) borrows mutable state The upstream binding owner is authoritative
ImagePicker EffectsPipeline (pipeline) stores or receives App/module collaborators

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.

Concern Source mechanism Verified placement or handoff Evidence
Queue scheduling DispatchQueue.main.async The source addresses the main dispatch queue. SubjectLiftingEffects/ContentView.swift:76
Queue scheduling DispatchQueue(label:) The source constructs a dispatch queue; its label alone does not prove a thread. SubjectLiftingEffects/EffectsPipeline.swift:48

@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

SubjectLiftingEffects/ContentView.swift:76 — representative execution boundary

                DispatchQueue.main.async {
                    pipeline.inputImage = image
                }

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.

Category Mechanism or module Verified role Evidence
State propagation SwiftUI state property wrapper A SwiftUI property wrapper supplies or observes UI state. SubjectLiftingEffects/ContentView.swift:14
State propagation ObservableObject ObservableObject supplies an observation contract. SubjectLiftingEffects/EffectsPipeline.swift:31
State propagation @Published A published property can emit owner-controlled changes. SubjectLiftingEffects/EffectsPipeline.swift:34
Source import SwiftUI The cited file imports this module; runtime use and architectural role are not inferred. SubjectLiftingEffects/ContentView.swift:8
Source import Combine The cited file imports this module; runtime use and architectural role are not inferred. SubjectLiftingEffects/EffectsPipeline.swift:9
Source import CoreImage The cited file imports this module; runtime use and architectural role are not inferred. SubjectLiftingEffects/EffectsPipeline.swift:10
Source import Foundation The cited file imports this module; runtime use and architectural role are not inferred. SubjectLiftingEffects/EffectsPipeline.swift:8
Source import PhotosUI The cited file imports this module; runtime use and architectural role are not inferred. SubjectLiftingEffects/ContentView.swift:9

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

SubjectLiftingEffects/SubjectLiftingEffectsApp.swift:12 — representative type boundary

@main
struct SubjectLiftingEffectsApp: App {
    // ...
    @StateObject private var pipeline = EffectsPipeline()
    // ...
}
Type Responsibility Depends on or conforms to
SubjectLiftingEffectsApp Application entry and top-level composition App
OutputView User-interface presentation and input forwarding View
ContentView User-interface presentation and input forwarding View
EffectsPipeline Coordinates a multi-stage processing flow ObservableObject
EffectPicker Represents a feature value or composable behavior View
BackgroundPicker Represents a feature value or composable behavior View
ImagePicker Represents a feature value or composable behavior View
SubImageContent Represents a feature value or composable behavior View
Effect Defines a closed set of feature states or choices String, Equatable, CaseIterable
Background Defines a closed set of feature states or choices String, Equatable, CaseIterable

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Symbol Access Verified effect Likely rationale
imageSelection (SubjectLiftingEffects/ContentView.swift:46) private Use is restricted to the lexical declaration and same-file extensions allowed by Swift. Inference: keep state mutation or dependency lifetime inside the owning implementation.
loadInputImage (SubjectLiftingEffects/ContentView.swift:57) private Use is restricted to the lexical declaration and same-file extensions allowed by Swift. Inference: hide an implementation step that is not part of the collaboration surface.
outputViewSize (SubjectLiftingEffects/ContentView.swift:120) private Use is restricted to the lexical declaration and same-file extensions allowed by Swift. Inference: keep state mutation or dependency lifetime inside the owning implementation.
processingQueue (SubjectLiftingEffects/EffectsPipeline.swift:48) private Use is restricted to the lexical declaration and same-file extensions allowed by Swift. Inference: keep state mutation or dependency lifetime inside the owning implementation.

Reference code

SubjectLiftingEffects/ContentView.swift:46 — representative boundary

struct ImagePicker: View {
    // ...
    @State private var imageSelection: PhotosPickerItem? = nil
    // ...
}

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

Logic Owning type or file Placement rationale
Application entry and top-level composition SubjectLiftingEffectsApp The source’s App suffix makes this role explicit.
Coordinates a multi-stage processing flow EffectsPipeline The source’s Pipeline suffix makes this role explicit.
User-interface presentation and input forwarding ContentView, OutputView The source’s View suffix makes this role explicit.

Design patterns

Pattern Source evidence Purpose or tradeoff
SwiftUI environment injection SubjectLiftingEffects/ContentView.swift:119 The environment supplies state or a capability without threading it through every initializer.
Binding-based state propagation SubjectLiftingEffects/ContentView.swift:14 A binding exposes controlled read/write access while the upstream owner remains authoritative.
Publisher-backed observable state SubjectLiftingEffects/EffectsPipeline.swift:37 Published properties notify observers while mutation remains with the state object.

Naming conventions

  • Types: App: SubjectLiftingEffectsApp; Pipeline: EffectsPipeline; View: ContentView, OutputView.
  • Protocols: no local protocol declaration in the scanned source.
  • Methods: loadInputImage, regenerate, apply, subjectMask, instances, image, loadImage, render.
  • Files: SubjectLiftingEffects/SubjectLiftingEffectsApp.swift, SubjectLiftingEffects/ContentView.swift, SubjectLiftingEffects/EffectsPipeline.swift.

Architecture takeaways

  • SubjectLiftingEffectsApp is the main source-visible entry or composition anchor for this sample.
  • Framework work reaches SwiftUI, CoreImage, PhotosUI, UIKit 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.
  • The source does not justify labeling the design protocol-oriented.

Source map

Source file Relevant symbols
SubjectLiftingEffects/SubjectLiftingEffectsApp.swift Cited implementation, SubjectLiftingEffectsApp
SubjectLiftingEffects/ContentView.swift Cited implementation, DispatchQueue.main.async, SwiftUI state property wrapper, SwiftUI, PhotosUI, EffectPicker, BackgroundPicker, ImagePicker, OutputView, SubImageContent, ContentView
SubjectLiftingEffects/EffectsPipeline.swift Cited implementation, DispatchQueue(label:), ObservableObject, @Published, Combine, CoreImage, Foundation, Effect, Background, EffectsPipeline