macOS Dynamic Wallpaper Generator - Creates HEIC wallpapers that switch between light/dark modes

DynamicWallpaperGenerator.swift

#!/usr/bin/swift

import Foundation
import AppKit
import AVFoundation
import ImageIO

struct Color {
    let r: CGFloat
    let g: CGFloat
    let b: CGFloat
    
    init?(hex: String) {
        let clean = hex.trimmingCharacters(in: CharacterSet(charactersIn: "#"))
        guard clean.count == 6, let value = Int(clean, radix: 16) else { return nil }
        
        self.r = CGFloat((value >> 16) & 0xFF) / 255.0
        self.g = CGFloat((value >> 8) & 0xFF) / 255.0
        self.b = CGFloat(value & 0xFF) / 255.0
    }
}

func createImage(color: Color, size: CGSize = CGSize(width: 5120, height: 2880)) -> CGImage? {
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let context = CGContext(
        data: nil,
        width: Int(size.width),
        height: Int(size.height),
        bitsPerComponent: 8,
        bytesPerRow: Int(size.width) * 4,
        space: colorSpace,
        bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue
    )
    
    context?.setFillColor(red: color.r, green: color.g, blue: color.b, alpha: 1.0)
    context?.fill(CGRect(origin: .zero, size: size))
    
    return context?.makeImage()
}

func createWallpaper(lightHex: String, darkHex: String, outputFile: String) throws {
    guard let lightColor = Color(hex: lightHex) else {
        throw NSError(domain: "", code: 1, userInfo: [NSLocalizedDescriptionKey: "Invalid light color: \(lightHex)"])
    }
    
    guard let darkColor = Color(hex: darkHex) else {
        throw NSError(domain: "", code: 2, userInfo: [NSLocalizedDescriptionKey: "Invalid dark color: \(darkHex)"])
    }
    
    guard let lightImage = createImage(color: lightColor) else {
        throw NSError(domain: "", code: 3, userInfo: [NSLocalizedDescriptionKey: "Failed to create light image"])
    }
    
    guard let darkImage = createImage(color: darkColor) else {
        throw NSError(domain: "", code: 4, userInfo: [NSLocalizedDescriptionKey: "Failed to create dark image"])
    }
    
    // Create metadata for appearance switching
    let metadata = CGImageMetadataCreateMutable()
    
    CGImageMetadataRegisterNamespaceForPrefix(
        metadata,
        "http://ns.apple.com/namespace/1.0/" as CFString,
        "apple_desktop" as CFString,
        nil
    )
    
    let appearanceData = try JSONEncoder().encode([
        "ap": ["l": 0, "d": 1]  // light index: 0, dark index: 1
    ])
    
    let plistData = try PropertyListSerialization.data(
        fromPropertyList: try JSONSerialization.jsonObject(with: appearanceData),
        format: .binary,
        options: 0
    )
    
    let tag = CGImageMetadataTagCreate(
        "http://ns.apple.com/namespace/1.0/" as CFString,
        "apple_desktop" as CFString,
        "apr" as CFString,
        .string,
        plistData.base64EncodedString() as CFString
    )
    
    CGImageMetadataSetTagWithPath(metadata, nil, "apple_desktop:apr" as CFString, tag!)
    
    // Create HEIC file
    let outputData = NSMutableData()
    let destination = CGImageDestinationCreateWithData(
        outputData,
        AVFileType.heic as CFString,
        2,
        nil
    )!
    
    CGImageDestinationAddImageAndMetadata(
        destination,
        lightImage,
        metadata,
        [kCGImageDestinationLossyCompressionQuality: 1.0] as CFDictionary
    )
    
    CGImageDestinationAddImage(
        destination,
        darkImage,
        [kCGImageDestinationLossyCompressionQuality: 1.0] as CFDictionary
    )
    
    guard CGImageDestinationFinalize(destination) else {
        throw NSError(domain: "", code: 5, userInfo: [NSLocalizedDescriptionKey: "Failed to create HEIC"])
    }
    
    try outputData.write(to: URL(fileURLWithPath: outputFile))
}

func printUsage() {
    print("""
    Usage: \(CommandLine.arguments[0]) [light_color] [dark_color] [output_file]
    
    Creates a macOS dynamic wallpaper that switches between light and dark colors.
    
    Arguments:
      light_color   Hex color for light mode (default: f0f0f0)
      dark_color    Hex color for dark mode (default: 1e1e1e)
      output_file   Output filename (default: wallpaper.heic)
    
    Examples:
      \(CommandLine.arguments[0])                                  # Modus colors
      \(CommandLine.arguments[0]) ffffff 000000                    # Black and white
      \(CommandLine.arguments[0]) fdf6e3 002b36 solarized.heic     # Solarized theme
    
    Colors can be specified with or without '#' prefix.
    """)
}

// Main
let args = CommandLine.arguments

if args.count > 1 && (args[1] == "-h" || args[1] == "--help") {
    printUsage()
    exit(0)
}

let lightHex = args.count > 1 ? args[1] : "f0f0f0"  // Modus Operandi bg-dim
let darkHex = args.count > 2 ? args[2] : "1e1e1e"   // Modus Vivendi bg-dim
let outputFile = args.count > 3 ? args[3] : "wallpaper.heic"

do {
    try createWallpaper(lightHex: lightHex, darkHex: darkHex, outputFile: outputFile)
} catch {
    print("Error: \(error.localizedDescription)")
    exit(1)
}