C#采用画图方式生成验证码样式图片

本文是关注如何使用Graphics生成验证码样式，效果如图：

1. 用C#创建一个基于Windows Form的应用程序；

2. 拖一个【pictureBox】到窗体中，双击该控件，在Click动作中添加，每次点击效果不一样：

        private void pictureBox1_Click(object sender, EventArgs e)
        {
            Random r = new Random(); 
            string[] fontString = new string[] { "黑体", "幼圆", "楷体", "华文仿宋"};
            Color[] colorArray = new Color[] { Color.Blue, Color.Black, Color.Yellow, Color.Green};

            string strNumbers = "";

            Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            Graphics g = Graphics.FromImage(bmp);

            //生成4个数字、点、字体、颜色，画出来
            for(int i=0; i<4; i++)
            {
                strNumbers += r.Next(0, 9);

                Point pt = new Point(i * 20, 0);
                g.DrawString(strNumbers[i].ToString(), new Font(fontString[i], 20), 
                    new SolidBrush(colorArray[r.Next(3)]), pt);
            }

            //随机画几条直线
            for (int i = 0; i < 10; 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(colorArray[i % 4]), p1, p2);
            }

            //随机画一些点
            for (int i = 0; i < 200; i++ )
            {
                bmp.SetPixel(r.Next(bmp.Width), r.Next(bmp.Height), colorArray[i % 4]);
            }
            pictureBox1.Image = bmp;
        }