用GDI+画验证码

1、新建一个窗体应用程序，在上面拖一个pictureBox对象，为其添加单击事件

2、创建GDI对象、产生随机数画入图片中、画线条、最后将图片到pictureBox中，代码如下：

  private void pictureBox1_Click(object sender, EventArgs e)
         {
             //创建GDI对象
             Bitmap bmp = new Bitmap(,);
             Graphics g = Graphics.FromImage(bmp);

            //产生随机数并画入图片中
             Random r = new Random();
             string str = "";
             for (int i = ; i < ;i++ )
             {
                 str += r.Next(,);
             }
             for (int i = ; i < ; i++)
             {
                 Point p = new Point(i*,);
                 string[] fonts = { "微软雅黑", "宋体", "黑体", "隶书", "仿宋" };
                 Color[] colors = { Color.Yellow,Color.Blue,Color.Black,Color.Red,Color.Pink};
                 g.DrawString(str[i].ToString(),new Font(fonts[r.Next(,)],,FontStyle.Bold),new SolidBrush(colors[r.Next(,)]),p);

             }

             //画线
             for (int i = ; i < ; i++)
             {
                 Point p1 = new Point(r.Next(,bmp.Width),r.Next(,bmp.Height));
                 Point p2 = new Point(r.Next(,bmp.Width),r.Next(,bmp.Height));
                 g.DrawLine(new Pen(Brushes.Green),p1,p2);
             }

             //将图片镶嵌到pictureBox中
             pictureBox1.Image = bmp;

         }