Loewensberg concentric circles

#r "System.Drawing.dll"
#r "System.Windows.Forms.dll"

open System
open System.Drawing
open System.Drawing.Drawing2D
open System.Windows.Forms

let width, height = 512, 512

let white = 229,233,225
let yellow = 230, 202, 59
let sand = 224, 158, 1
let orange = 240, 104, 54
let red = 234, 67, 78

let blue1 = 122, 139, 254
let blue2 = 138, 121, 213
let purple = 166, 114, 192

let toPen (r,g,b) =
   new Pen(Color.FromArgb(255,r,g,b))

let toBrush (r,g,b) =
   let color = Color.FromArgb(255,r,g,b)
   new SolidBrush(color)

let draw (n1:int) (n2:int) =
   let image = new Bitmap(width, height)
   use graphics = Graphics.FromImage(image)
   graphics.SmoothingMode <- System.Drawing.Drawing2D.SmoothingMode.AntiAlias
   let brush = toBrush white
   graphics.FillRectangle(brush, 0, 0, width, height)

   [yellow;sand;orange;red;white]
   |> List.iteri (fun i color ->
      let brush = toBrush color
      let k = 40+i*30
      graphics.FillPie(brush,k,k,width-k*2,height-k*2,0,360)
   )

   [red; purple; blue2; blue1 ;white]
   |> List.iteri (fun i color ->
      let brush = toBrush color
      let k = 40+i*30
      let path = new GraphicsPath()
      path.AddLine(0,512, 0, 100)
      let x1, x2 = k+30+n1, k-30-n2+(width-k*2)
      path.AddLine(x1 ,  0, x1 ,256)
      path.AddLine(x1 ,256, x2 ,256)
      path.AddLine(x2 ,256, x2 ,  0)
      path.AddLine(x2 ,  0, 512, 0)
      path.AddLine(512, 0,  512,512)
      graphics.SetClip(path)
      graphics.FillPie(brush,k,k,width-k*2,height-k*2,0,360)
   )

   let brush = toBrush white
   let k = 40+4*30
   graphics.FillPie(brush,k,k,width-k*2,height-k*2,0,360)

   image

let show () =
   let image = draw 30 30
   let form = new Form (Text="Loewensberg Lines", Width=width+16, Height=height+36)
   let picture = new PictureBox(Dock=DockStyle.Fill, Image=image)
   image.Save(@"C:\app\Loewensberg Square.png", Imaging.ImageFormat.Png)
   do  form.Controls.Add(picture)
   form.ShowDialog() |> ignore

//show()

#r @"Gif.Components.dll"
open Gif.Components

let encoder = AnimatedGifEncoder()

if encoder.Start(@"c:\temp\Loewensberg circles shakeup.gif") then
   encoder.SetFrameRate(20.0f)
   encoder.SetRepeat 0
   for n = 0 to 15 do
      encoder.AddFrame(draw (15+n) (15-n)) |> ignore
   for n = 15 downto -15 do
      encoder.AddFrame(draw (15+n) (15-n)) |> ignore
   for n = -15 to 0 do
      encoder.AddFrame(draw (15+n) (15-n)) |> ignore
   for n = 15 to 45 do
      encoder.AddFrame(draw (n) (n)) |> ignore
   for n = 45 downto 0 do
      encoder.AddFrame(draw (n) (n)) |> ignore
   for n = 0 to 15 do
      encoder.AddFrame(draw (n) (n)) |> ignore
   encoder.Finish() |> ignore