c#验证码

 private void pictureBox1_Click(object sender, EventArgs e)
        {
            
            Random r = new Random();
            string str = null;
            for (int i = 0; i < 6; i++)
            {
                int rnumber = r.Next(0, 10);
                str += rnumber;
            }
            //创建GDI对象
            Bitmap bmp = new Bitmap(120, 25);
            Graphics g = Graphics.FromImage(bmp);
            for (int i = 0; i < 6; i++)
            {
                Point p = new Point(i * 15, 0);
                string[] Fonts = { "隶书", "仿宋", "华文行楷", "宋体", "微软雅黑" };
                Color[] colors = { Color.Red, Color.Black, Color.Blue, Color.DeepPink, Color.DimGray };
                g.DrawString(str[i].ToString(), new Font(Fonts[r.Next(0, 5)], 15, FontStyle.Bold), new SolidBrush(colors[r.Next(0, 5)]), p);
     
            }
            for (int i = 0; i < 15; i++)
            { 
                Point p1=new Point(r.Next(0,bmp.Width),r.Next(0,bmp.Height));
                 Point p2=new Point(r.Next(0,bmp.Width),r.Next(0,bmp.Height));
                 g.DrawLine(new Pen(Brushes.Green), p1, p2);

            }
            for (int i = 0; i <= 200; i++)
            {

                Point p1 = new Point(r.Next(0, bmp.Width), r.Next(0, bmp.Height));
                Point p2 = new Point(r.Next(0, bmp.Width), r.Next(0, bmp.Height));
                bmp.SetPixel(p1.X,p1.Y,Color.Black);

            }
                pictureBox1.Image = bmp;
        }