class CanvasViewModel: ObservableObject {

    @Published var documents: [Doc] = [Doc]()

    // MARK: - Properties
    let canvasWidth: Int = 256
    let canvasHeight: Int = 256

    /// Pixel per pixels 👀
    /// if canvasPixelFactor is high every pixels looks better (no antialiasing) but the performance in older devices will be compromised... Int(UIScreen.main.scale) + (3-12) works good
    let canvasPixelFactor: Int = Int(UIScreen.main.scale) + 3

    /// Computed canvas size
    var canvasWidthComputed: CGFloat {
        return CGFloat(canvasWidth * canvasPixelFactor)
    }

    var canvasHeightComputed: CGFloat {
        return CGFloat(canvasWidth * canvasPixelFactor)
    }
    .
    .
    .
}

private func createImage(completionHandler: @escaping (UIImage?, String?) -> Void){

        guard !documents.isEmpty else { fatalError() }

        guard canvasWidth > 0 && canvasHeight > 0 else { fatalError() }


        DispatchQueue.global(qos: .utility).async {
            let width = self.canvasWidth * self.canvasPixelFactor
            let height = self.canvasHeight * self.canvasPixelFactor
            let rgbColorSpace =     CGColorSpaceCreateDeviceRGB()
            let bitmapInfo =        CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue) // premultipliedLast or .none
            let bitsPerComponent =  8
            let bitsPerPixel =      32

            var pixels = [Pixel]()

            if self.pixelsArray.isEmpty {

                for _ in 0..<width {
                    for _ in 0..<height {
                        pixels.append(Pixel(r: 255, g: 255, b: 255, a: 255))
                    }
                }

                // Colorize
                for doc in self.documents {
                    let x = doc.x + 1
                    let y = doc.y + 1

                    let startXPx = x > 0 ? Int((x-1) * self.canvasPixelFactor) : 1
                    let endXPx = Int(x * self.canvasPixelFactor)

                    let startYPx = y > 0 ? Int((y-1) * self.canvasPixelFactor) : 1
                    let endYPx = Int(y * self.canvasPixelFactor)

                    for i in startXPx..<endXPx{
                        for j in startYPx..<endYPx{
                            let offset: Int = (Int(self.canvasWidthComputed) * j) + i
                            pixels[offset] = Pixel(hexString: doc.hex)
                        }
                    }
                }

                .
                .
                .
                .
    }