Save bitmap to stream routines used in the advent snowflake project

bitmapToStream.fs

//The flakes need to be a stream. Remember to dispose bitmaps :)
let bitmapSave (bitmap :Bitmap) =
      let stream = new System.IO.MemoryStream()
      bitmap.Save(stream, Imaging.ImageFormat.Png)
      bitmap.Dispose()
      stream.Position <- 0L
      stream
      
//we need a graphics object to draw with and a bitmap to save onto.
//Return a tuple of graphics with its associated bitmmap
let getGraphics (h:int)(w:int) (p:int) =
      let bitmap = new Bitmap(w + p,h + p)
      let g = Graphics.FromImage(bitmap)
      g.SmoothingMode <- Drawing2D.SmoothingMode.AntiAlias
      g.TextRenderingHint <- Text.TextRenderingHint.ClearTypeGridFit
      g.Clear(Color.Transparent)
      (g ,bitmap)