Sample CodemacOSReviewed 2026-07-21View on Apple Developer

Calculating the dominant colors in an image

At a glance

Item Summary
Purpose Find the main colors in an image by implementing k-means clustering using the Accelerate framework.
App architecture A Swift sample with the source-visible chain AccelerateKMeansAppContentViewAccelerate APIs.
Main patterns SwiftUI environment injection, Publisher-backed observable state
Project style 6 scanned source file(s) across Swift, organized around ranked entry, type, and file boundaries.

Project structure

Source bundle/
├── accelerate-k-means/
│   ├── AccelerateKMeansApp.swift
│   ├── ContentView.swift
│   ├── kMeansCalculatorStructures.swift
│   ├── kMeansCalculatorUtilityFunctions.swift
│   ├── kMeansCalculator.swift
│   ├── KMeansCalculatorSceneKitFunctions.swift
│   └── accelerate_k_means.entitlements
├── Configuration/
│   └── SampleCode.xcconfig
└── accelerate-k-means.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 4 project/configuration file(s) and 6 source declaration(s).

Overall architecture

Reference code

accelerate-k-means/AccelerateKMeansApp.swift:10 — architecture anchor

@main
struct AccelerateKMeansApp: App {
    // ...
}

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 Accelerate.

Ownership and state

Ownership evidence

accelerate-k-means/AccelerateKMeansApp.swift:13 — stored dependency or nearest verified ownership anchor

@main
struct AccelerateKMeansApp: App {
    // ...
    @StateObject private var kMeansCalculator = KMeansCalculator()
    // ...
}
Owner Object or state Relationship Mutation authority
AccelerateKMeansApp KMeansCalculator (kMeansCalculator) owns wrapper-managed state Owning lexical scope
ContentView KMeansCalculator (kMeansCalculator) receives environment-provided state The environment provider is authoritative
Centroid Float (red) owns value state App/module collaborators
Centroid Float (green) owns value state 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.

Class and protocol design

accelerate-k-means/AccelerateKMeansApp.swift:11 — representative type boundary

struct AccelerateKMeansApp: App {
    // ...
}
Type Responsibility Depends on or conforms to
AccelerateKMeansApp Application entry and top-level composition App
ContentView User-interface presentation and input forwarding View
Centroid Represents a feature value or composable behavior Concrete collaborators/imported frameworks
DominantColor Represents a feature value or composable behavior Identifiable, Comparable
Thumbnail Represents a feature value or composable behavior Identifiable, Hashable
KMeansCalculator Owns feature behavior and collaborator lifecycle ObservableObject

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
kMeansCalculator (accelerate-k-means/AccelerateKMeansApp.swift:13) 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.
ContentView (accelerate-k-means/ContentView.swift:8) implicit internal No explicit modifier means the Swift declaration is internal to the module. Inference: app-target collaboration needs no exported library surface.

Reference code

accelerate-k-means/AccelerateKMeansApp.swift:13 — representative boundary

@main
struct AccelerateKMeansApp: App {
    // ...
    @StateObject private var kMeansCalculator = KMeansCalculator()
    // ...
}

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 AccelerateKMeansApp The source’s App suffix makes this role explicit.
User-interface presentation and input forwarding ContentView The source’s View suffix makes this role explicit.

Design patterns

Pattern Source evidence Purpose or tradeoff
SwiftUI environment injection accelerate-k-means/ContentView.swift:13 The environment supplies state or a capability without threading it through every initializer.
Publisher-backed observable state accelerate-k-means/kMeansCalculator.swift:37 Published properties notify observers while mutation remains with the state object.

Naming conventions

  • Types: App: AccelerateKMeansApp; View: ContentView.
  • Protocols: no local protocol declaration in the scanned source.
  • Methods: populateDistances, makeCentroidIndices, generateThumbnailRepresentations, weightedRandomIndex, distanceSquared, subtract, saturate, allocateDistancesBuffer.
  • Files: accelerate-k-means/AccelerateKMeansApp.swift, accelerate-k-means/ContentView.swift.

Architecture takeaways

  • AccelerateKMeansApp is the main source-visible entry or composition anchor for this sample.
  • Framework work reaches SceneKit, SwiftUI, Accelerate, Cocoa 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
accelerate-k-means/AccelerateKMeansApp.swift AccelerateKMeansApp
accelerate-k-means/ContentView.swift ContentView
accelerate-k-means/kMeansCalculatorStructures.swift Centroid, DominantColor, Thumbnail
accelerate-k-means/kMeansCalculatorUtilityFunctions.swift Feature implementation
accelerate-k-means/kMeansCalculator.swift KMeansCalculator
accelerate-k-means/KMeansCalculatorSceneKitFunctions.swift Feature implementation