Declarative flag filters with CoreImage

flags.swift

//
//  Because you're not going to put yet another asset in your bundle, are you?
//
//  Created by Ben Torkington on 1/08/23.
//

import CoreImage

class FlagFilter {
    let displayName: String
    let baseImage: CIImage
    private let components = 4
    private let width: Int
    private let height: Int

    init(name: String, pixelData: [UInt8], width: Int, height: Int) {
        self.displayName = name
        self.width = width
        self.height = height

        baseImage = CIImage(
            bitmapData: Data(pixelData),
            bytesPerRow: width * components,
            size: CGSize(width: width, height: height),
            format: CIFormat.ARGB8,
            colorSpace: CGColorSpaceCreateDeviceRGB()
        ).samplingNearest()
    }

    func filter(image: CIImage) -> CIImage {
        return baseImage
            .transformed(by: CGAffineTransform(
                scaleX: image.extent.width / CGFloat(width),
                y: image.extent.height / CGFloat(height)))
            .composited(over: image)
    }
}

class PrideFlag: FlagFilter { // 🏳️‍🌈
    let alpha = UInt8(192)

    init() {
        let palette: [UInt8] = [
            alpha, 255, 0, 24,      // Vivid Red
            alpha, 255, 165, 44,    // Deep Saffron
            alpha, 255, 255, 65,    // Maximum Yellow
            alpha, 0, 128, 24,      // Ao
            alpha, 0, 0, 249,       // Blue
            alpha, 134, 0, 125,     // Philippine Violet
        ]

        super.init(name: "Pride Flag", pixelData: palette, width: 6, height: 1)
    }
}

class TransgenderFlag: FlagFilter { // 🏳️‍⚧️
    let alpha = UInt8(192)

    init() {
        let palette: [UInt8] = [
            alpha, 85, 205, 252,     // Maya Blue
            alpha, 247, 168, 184,    // Amaranth Pink
            alpha, 255, 255, 255,    // White
            alpha, 247, 168, 184,    // Amaranth Pink
            alpha, 85, 205, 252,     // Maya Blue
        ]

        super.init(name: "Transgender Flag", pixelData: palette, width: 1, height: 5)
    }
}