let private func_f x = (x + 1.0) * (x + 1.0) / 5.0
let private func_i x = (x + 1) * (x + 1) / 5

let private toFloat_0 (n : int) = Convert.ToDouble(n)
let private toFloat_1 (n : int, f : int) =
    Convert.ToDouble(n) +
    Convert.ToDouble(f) / 10.0
let private toFloat_2 (n : int, f1 : int, f2 : int) =
    Convert.ToDouble(n) +
    Convert.ToDouble(f1) / 10.0 +
    Convert.ToDouble(f1) / 100.0
let private toFloat_3 (n : int, f1 : int, f2 : int, f3 : int) =
    Convert.ToDouble(n) +
    Convert.ToDouble(f1) / 10.0 +
    Convert.ToDouble(f1) / 100.0 +
    Convert.ToDouble(f1) / 1000.0

let private half n = n / 2

let private DrawBack image =
    let res : Bitmap = image
    let h = image.Height
    let w = image.Width
    for x = 0 to w - 1 do
        res.SetPixel(x, half h, Color.Gray)
    for y = 0 to h - 1 do
        res.SetPixel(half w, y, Color.Gray)
    res

let private isDraw (x, y, h, w) =
    if ((x <= 0) || (x >= w)) then false
    else
        if ((y <= 0) || (y >= h)) then false
        else
            true

let Draw_0 (image : Bitmap) =
    let (res : Bitmap) = DrawBack image
    let h = res.Height
    let w = res.Width
    let pos_x x = x + half w
    let pos_y y = (half h) - y

    for x = -(half w) to (half w) do
            let y = func_i x
            if isDraw ((pos_x x), (pos_y y), h, w) then
                res.SetPixel(pos_x x, pos_y y, Color.Red)
    res

let Draw_1 (image : Bitmap) =
    let (res : Bitmap) = DrawBack image
    let h = res.Height
    let w = res.Width
    let pos_x x = x + half w
    let pos_y y = (half h) - y

    for x = -(half w) to (half w) do
        for f = 0 to 9 do
            let tx = toFloat_1(x, f)
            let ty = Math.Round(func_f tx)
            let y = Convert.ToInt32(ty)
            if isDraw ((pos_x x), (pos_y y), h, w) then
                res.SetPixel(pos_x x, pos_y y, Color.Red)
    res

let Draw_2 (image : Bitmap) =
    let (res : Bitmap) = DrawBack image
    let h = res.Height
    let w = res.Width
    let pos_x x = x + half w
    let pos_y y = (half h) - y

    for x = -(half w) to (half w) do
        for f1 = 0 to 9 do
            for f2 = 0 to 9 do
                let tx = toFloat_2(x, f1, f2)
                let ty = Math.Round(func_f tx)
                let y = Convert.ToInt32(ty)
                if isDraw ((pos_x x), (pos_y y), h, w) then
                    res.SetPixel(pos_x x, pos_y y, Color.Red)
    res

let Draw_3 (image : Bitmap) =
    let (res : Bitmap) = DrawBack image
    let h = res.Height
    let w = res.Width
    let pos_x x = x + half w
    let pos_y y = (half h) - y

    for x = -(half w) to (half w) do
        for f1 = 0 to 9 do
            for f2 = 0 to 9 do
                for f3 = 0 to 9 do
                    let tx = toFloat_3(x, f1, f2, f3)
                    let ty = Math.Round(func_f tx)
                    let y = Convert.ToInt32(ty)
                    if isDraw ((pos_x x), (pos_y y), h, w) then
                        res.SetPixel(pos_x x, pos_y y, Color.Red)
    res

//-----------------------------------------------------------------------------------

let private toFloat_3 (n : int, f1 : int, f2 : int, f3 : int) =
    Convert.ToDouble(n) +
    Convert.ToDouble(f1) / 10.0 +
    Convert.ToDouble(f1) / 100.0 +
    Convert.ToDouble(f1) / 1000.0

let Draw_3 (image : Bitmap) =
    let (res : Bitmap) = DrawBack image
    let h = res.Height
    let w = res.Width
    let pos_x x = x + half w
    let pos_y y = (half h) - y

    for x = -(half w) to (half w) do
        for f1 = 0 to 9 do
            for f2 = 0 to 9 do
                for f3 = 0 to 9 do
                    let tx = toFloat_3(x, f1, f2, f3)
                    let ty = Math.Round(func_f tx)
                    let y = Convert.ToInt32(ty)
                    if isDraw ((pos_x x), (pos_y y), h, w) then
                        res.SetPixel(pos_x x, pos_y y, Color.Red)
    res