Improving the quality of quantized images with dithering

At a glance

Project structure

Source bundle/
├── ImageDither/
│   ├── ImageDitherApp.swift
│   ├── ImageDitherEngine.swift
│   ├── ContentView.swift
│   └── ImageDither.entitlements
├── Configuration/
│   └── SampleCode.xcconfig
└── Saturation-Adjust-in-YCbCr.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 4 source declaration(s).

Overall architecture

flowchart LR
    N1["ImageDitherApp"]
    N2["ContentView"]
    N3["ImageDitherEngine"]
    N4["Accelerate APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

ImageDither/ImageDitherApp.swift:10 — architecture anchor

@main
struct ImageDitherApp: 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

classDiagram
    ImageDitherApp *-- ImageDitherEngine : imageDitherEngine
    ImageDitherEngine o-- vImage_Buffer : sourceBuffer
    ImageDitherEngine o-- vImage_Buffer : destinationBuffer
    ImageDitherEngine o-- CGImage : emptyCGImage

Ownership evidence

ImageDither/ImageDitherApp.swift:13 — stored dependency or nearest verified ownership anchor

@main
struct ImageDitherApp: App {
    // ...
    @StateObject private var imageDitherEngine = ImageDitherEngine()
    // ...
}

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

ImageDither/ImageDitherApp.swift:11 — representative type boundary

struct ImageDitherApp: App {
    // ...
}

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

Access control

Reference code

ImageDither/ImageDitherApp.swift:13 — representative boundary

@main
struct ImageDitherApp: App {
    // ...
    @StateObject private var imageDitherEngine = ImageDitherEngine()
    // ...
}

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: App: ImageDitherApp; Engine: ImageDitherEngine; View: ContentView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: applyImageDither.
• Files: ImageDither/ImageDitherApp.swift, ImageDither/ImageDitherEngine.swift, ImageDither/ContentView.swift.

Architecture takeaways

• ImageDitherApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches 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

• Official Apple documentation