     private func symbolFromIntensity(intensity: Double) -> String
     {
         assert(0.0 <= intensity && intensity <= 1.0)
+        
         let
         factor = palette.symbols.count - 1,
         value  = round(intensity * Double(factor)),

{
    private let
    image:   UIImage,
    width:   Int,
    height:  Int,
    palette: AsciiPalette
    
    init(_ image: UIImage, _ palette: AsciiPalette)
    {
        self.image   = image
        self.width   = Int(image.size.width)
        self.height  = Int(image.size.height)
        self.palette = palette
    }
    

    
    private func intensityMatrixFromPixelPointer(pointer: PixelPointer) -> [[Double]]
    {
        let
        width  = Int(image.size.width),
        height = Int(image.size.height),
        matrix = Pixel.createPixelMatrix(width, height)
        return matrix.map { pixelRow in
            pixelRow.map { pixel in
                pixel.intensityFromPixelPointer(pointer)
