private void Form1_Load(object sender, EventArgs e)
        {
            menu.Items.Add("item1");
            menu.Items.Add("item2");
            menu.Items.Add("item3");
        }
        Bitmap bmp = new Bitmap(@"C:\Users\SaeWind\Desktop\123\1.png");
        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g=e.Graphics;
            g.DrawImage(bmp,pictureBox1.Bounds);
        }
        ContextMenuStrip menu = new ContextMenuStrip();
        private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Right)
            {
                Point t =PointToScreen(e.Location);
                menu.Show(t.X,t.Y);
            }
        }

        private void pictureBox1_SizeChanged(object sender, EventArgs e)
        {
            ((Control)sender).Refresh();
        }