Change a PictureBox dynamically

gistfile1.cs

  public partial class MapForm2 : Form
  {
    private Bitmap map_t;
    private Bitmap map;

    public MapForm2()
    {
      InitializeComponent();
      var size = Properties.Resources.Penguins.Size;
      map_t = new Bitmap("map.gif", true);
      map = new Bitmap(map_t.Width, map_t.Height);
      MapCanvas.Image = map;
    }

    private void MapCanvas_MouseUp(object sender, MouseEventArgs e)
    {
      var rect = new Rectangle(e.X - 3, e.Y - 3, 7, 7);
      using (var g = Graphics.FromImage(map))
      {
        g.FillEllipse(Brushes.Red, rect);
      }

      MapCanvas.Invalidate();
    }
  }