private void button3_Click(object sender, EventArgs e)
        {
            //this.BackColor = Color.FromArgb(128, 140, 75);
            MakeTransparent(System.Windows.Forms.Application.StartupPath + @"/NonTransparent.png", System.Windows.Forms.Application.StartupPath + @"/Transparent.png");
        }

        private static void MakeTransparent(string inputFileName, string outputFileName)
        {
            Bitmap bmpIn = (Bitmap)Bitmap.FromFile(inputFileName);
            Bitmap converted = new Bitmap(bmpIn.Width, bmpIn.Height, PixelFormat.Format32bppArgb);
            using (Graphics g = Graphics.FromImage(converted))
            {
                // Prevent DPI conversion
                // g.PageUnit = GraphicsUnit.Pixel;
                /*
                g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
                 */
                // Draw the image
                //g.DrawImageUnscaled(bmpIn, 0, 0);
                g.DrawImage(bmpIn, 0, 0);
            }
            //converted.MakeTransparent(converted.GetPixel(0, 0));
            converted.MakeTransparent(Color.FromArgb(128, 140, 75));
            converted.Save(outputFileName, ImageFormat.Png);
            converted.Dispose();
            bmpIn.Dispose();
        }