ASP.NET - Impresion de Puntos sobre Imagen Asp.net

'Coger la imagen inicial

Dim bitmapImagen As New System.Drawing.Bitmap(Server.MapPath(aspImage.ImageUrl))

'Dibujar puntos

bitmapImagen.SetPixel(10, 10, System.Drawing.Color.Red)

bitmapImagen.SetPixel(12, 14, System.Drawing.Color.Yellow)

bitmapImagen.SetPixel(14, 12, System.Drawing.Color.Orange)

bitmapImagen.SetPixel(5, 5, System.Drawing.Color.Blue)

'Dibujar una línea

Dim grafico As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(bitmapImagen)

grafico.DrawLine(New System.Drawing.Pen(System.Drawing.Color.Red), New System.Drawing.Point(20, 20), New System.Drawing.Point(100, 50))

'Pintar la nueva imagen

Dim memoryStream As New System.IO.MemoryStream()

bitmapImagen.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Png)

Dim datosEnBase64 = Convert.ToBase64String(memoryStream.ToArray())

aspImage.ImageUrl = "data:image/png;base64," + datosEnBase64

<asp:Image runat="server" ID="aspImage" ImageUrl="Images/imagen.jpg"  />