Прозрачная панелька

Bitmap BackPanel;
        Panel LPanel;
        private void button1_Click(object sender, EventArgs e)
        {
            LPanel = new Panel { Location = new Point(0, 0), Width = 100, Height = this.Height };
            BackPanel = new Bitmap(LPanel.Width, LPanel.Height);
            this.DrawToBitmap(BackPanel, new Rectangle(0, 0, this.Width, this.Height));
            int X = Convert.ToInt32(((float)Width - (float)ClientSize.Width) / 2);
            int Y = SystemInformation.CaptionHeight + X;
            Cut(ref BackPanel, new Rectangle(X, Y, LPanel.Width, LPanel.Height));
            using (Graphics g = Graphics.FromImage(BackPanel))
            {
                SolidBrush Brush = new SolidBrush(Color.FromArgb(100, 0, 0, 0));
                g.FillRectangle(Brush, 0, 0, BackPanel.Width, BackPanel.Height);
            }
            LPanel.BackgroundImage = BackPanel;
            this.Controls.Add(LPanel);
        }
        private void button2_Click(object sender, EventArgs e)
        {
            this.Controls.Remove(LPanel);
        }
 
        private void Cut(ref Bitmap img, Rectangle cutRect)
        {
            if (cutRect.Width == 0 || cutRect.Height == 0) return;
 
            var rect = new Rectangle(0, 0, cutRect.Width, cutRect.Height);
 
            var path = new GraphicsPath();
            path.AddRectangle(rect);
 
            var res = new Bitmap(rect.Width, rect.Height);
            using (var gr = Graphics.FromImage(res))
            {
                gr.SetClip(path, CombineMode.Intersect);
                gr.DrawImage(img, -cutRect.Left, -cutRect.Top);
            }
            img.Dispose();
            img = res;
        }

BackPanel = new Bitmap(Width, Height);