Flag filters with CoreImage and Swift

flag-filters-with-CIImage.swift

class FlagFilter: FPFilter {
    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 {
        // todo: this filter never knows which way is 'up'

        // consider using CIBlendWithMask if we need to vary the alpha at runtime
        return baseImage
            .transformed(by: CGAffineTransform(
                scaleX: image.extent.width / CGFloat(width),
                y: image.extent.height / CGFloat(height)))
            .composited(over: image)
    }
}

class PrideFlag: FlagFilter { // 🏳️‍🌈
    let width = 6, height = 1, components = 4
    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)
    }
}

extension CIImage {
    func getCenter() -> CIVector {
        let extent = self.extent
        return CIVector(x: extent.origin.x + extent.size.width / 2, y: extent.origin.y + extent.size.height / 2)
    }
}

Don't worry about FPFilter, it's just a protocol from a wider part of one of my apps. Just use FlagFilter as a base class.