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(150,40);
            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 = 0; i < 5;i++ )
            {
                str += r.Next(0,10);
            }
            for (int i = 0; i < 5; i++) 
            {
                Point p = new Point(i*20,0);
                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(0,5)],20,FontStyle.Bold),new SolidBrush(colors[r.Next(0,5)]),p);
            
            }

            //画线
            for (int i = 0; i < 20; 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);
            }

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

        }