笔记11：GDI 制作数字验证码

　　　　大二学长让我学下GDI绘制验证码，然后自己就试了试了。找了点视频看了下。

　　　　现在会画直线，矩形，字符串，制作验证码

　　　　一、绘制一条直线

         private void button1_Click(object sender, EventArgs e)
         {
             Graphics g = this.CreateGraphics();     //实例化
             Pen pen = new Pen(Color.Black);         //创建一只笔，颜色
             Point p1 = new Point(, );           //两点确定一条直线
             Point p2 = new Point(,);
             g.DrawLine(pen,p1,p2);                  //画直线了
         }

　　　　二、绘制一个矩形，一个字符串

         private void button2_Click(object sender, EventArgs e)
         {
             Graphics j = this.CreateGraphics();
             Pen pen = new Pen(Color.YellowGreen);

             j.DrawRectangle(pen,,,,);     //矩形
             j.DrawString("管星，还蛮不错的！",new Font("宋体",,FontStyle.Bold),Brushes.Red,,);  //字符串
         }

　　　　三、制作验证码，和字符串升级版

　　　　

         string yanzheng = "";
         public void huantu()
         {
             //随机生成一个，四个数字的字符串
             Random r = new Random();
             string str = "";
             for (int i = ; i < ; i++)
             {
                 str = str + r.Next(, ).ToString();
             }
             yanzheng = str;
             //创建GDI对象
             Bitmap bmp = new Bitmap(100, 30);
             Graphics g = Graphics.FromImage(bmp);
             int n = ;
             //将数字画进图片中，随机的字体，随机的颜色
             for (int i = ; i < ; i++)
             {
                 string[] fonts = { "微软雅黑", "宋体", "幼圆", "黑体", "仿宋" };
                 Color[] colors = { Color.PowderBlue, Color.Green, Color.Blue, Color.Black, Color.Red };
                 g.DrawString(str[i].ToString(), new Font(fonts[r.Next(, )], , FontStyle.Bold), new SolidBrush(colors[r.Next(, )]), n, );
                 n += ;
             }
             //加干扰的点，
             for (int i = ; i < ; i++)
             {
                 Point p = new Point(r.Next(0, bmp.Width), r.Next(0, bmp.Height));
28                 bmp.SetPixel(p.X, p.Y, Color.Black);
             }
             //将图片镶嵌picturebox中
             pictureBox1.Image = bmp;
         }
         //看不清，换一张
         private void button2_Click(object sender, EventArgs e)
         {
             huantu();
         }
         private void button1_Click(object sender, EventArgs e)
         {
             if (yanzheng==this.textBox1.Text)
             {
                 MessageBox.Show("您输入的验证码正确！","消息提示");
             }
             else
             {
                 MessageBox.Show("您输入的验证码不正确！", "消息提示");
             }
         }
     }
 }