private void button35_Click_1(object sender, EventArgs e)
{
    Form form = new Form();
    //form.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
    //form.MaximizeBox = false;
    //form.MinimizeBox = false;
    //form.ControlBox = false;
    form.BackColor = Color.Fuchsia;
    form.TransparencyKey = form.BackColor;
    form.BackgroundImage = Image.FromFile("D:\\pie.png");
    form.Paint += form_Paint;
    //form.MouseDown += form_MouseDown;
    form.Show();
}

void form_Paint(object sender, PaintEventArgs e)
{
    using (Image img = Image.FromFile("D:\\proj.png"))
    e.Graphics.DrawImage(img, Point.Empty);
}

//void form_MouseDown(object sender, MouseEventArgs e)
//{
//    if (e.Button == MouseButtons.Left)
//    {
//        ReleaseCapture();
//        SendMessage( ((Form)sender).Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0);
//    }
//}

//public const int WM_NCLBUTTONDOWN = 0xA1;
//public const int HT_CAPTION = 0x2;
//[DllImportAttribute("user32.dll")]
//public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
//[DllImportAttribute("user32.dll")]
//public static extern bool ReleaseCapture();