Colorblinds

A Swift Package for simulating color blindness in iOS apps. Uses GPU-accelerated color transformation for real-time, full frame rate simulation.

Requirements

• iOS 17+
• Swift 5.9+

Installation

Add Colorblinds to your project via Swift Package Manager:

https://github.com/jdekock/Colorblinds

Or add it to your Package.swift:

dependencies: [
    .package(url: "https://github.com/jdekock/Colorblinds", from: "2.0.0")
]

Example

Normal	Picker	Tritanopia	Achromatopsia

Usage

SwiftUI

Apply a specific simulation:

import Colorblinds

struct ContentView: View {
    var body: some View {
        MyAppView()
            .colorBlindSimulation(.deuteranopia)
    }
}

Bind to an optional type (nil removes the filter):

@State private var selectedType: ColorBlindType?

var body: some View {
    MyAppView()
        .colorBlindSimulation(selectedType)
}

Full simulator experience — triple-tap anywhere to open a picker sheet:

var body: some View {
    MyAppView()
        .colorBlindSimulator()
}

Note: Apply the modifier to your content views rather than to a NavigationStack or TabView. These container views use internal rendering (e.g. navigation bar materials) that conflicts with the Metal shader, resulting in a yellow warning screen.

UIKit

Full simulator experience — call start with your app's window, then triple-tap to open a picker:

import Colorblinds

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options: UIScene.ConnectionOptions) {
    guard let windowScene = scene as? UIWindowScene,
          let window = windowScene.windows.first else { return }

    ColorBlindOverlay.shared.start(in: window)
}

Direct control:

// Apply a specific simulation
ColorBlindOverlay.shared.simulate(.protanopia, in: window)

// Remove the simulation
ColorBlindOverlay.shared.stop()

Supported Types

Type	Description
deuteranomaly	Reduced green sensitivity (most common)
deuteranopia	No green cones
protanomaly	Reduced red sensitivity
protanopia	No red cones
tritanomaly	Reduced blue sensitivity
tritanopia	No blue cones
achromatomaly	Reduced overall color sensitivity
achromatopsia	Complete color blindness

How It Works

• SwiftUI — Uses a [[stitchable]] Metal shader via .colorEffect(), running directly in SwiftUI's render pipeline. No screen capture, no overlay. Truly live at full frame rate.
• UIKit — Uses CADisplayLink to capture the window's layer, applies a CIColorMatrix filter on the GPU, and renders the result to an MTKView overlay.

License

MIT