生成验证码_pb 生成公式验证码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Text;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace CAPTCHA
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        /// <summary>
        /// 实现点一下就换一张验证码
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void pbCaptcha_Click(object sender, EventArgs e)
        {
            Bitmap bmp = new Bitmap(120, 40);
            Graphics g = Graphics.FromImage(bmp);
            Random r = new Random();
            
            string str = "";
            for (int i = 0; i < 5; i++)
            {
                int rNum=  r.Next(0, 10);
                str += rNum;
            }
 
            string[] fonts ={"华文行楷","微软雅黑","楷体","仿宋","宋体"};
            Color[] colors = { Color.Red,Color.RosyBrown,Color.DarkOrange,Color.SteelBlue,Color.DarkTurquoise};
 
            //随机字体
            InstalledFontCollection fc = new InstalledFontCollection();
            FontFamily[] fs = fc.Families;
           
            for (int i = 0; i < 5; i++)
            {
                Point p = new Point(i * 20, 0);
                g.DrawString(str[i].ToString(), new Font(fs[r.Next(0,fs.Length)],20,FontStyle.Bold), new SolidBrush(colors[i]), p);
            }
 
            //画50条线
            for (int i = 0; i < 40; 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(Color.LightGray),p1, p2);
            }
 
            //画50个点
            for (int i = 0; i < 50; i++)
            {
                Point p = new Point(r.Next(0, bmp.Height), r.Next(0, bmp.Width));
                bmp.SetPixel( p.Y,p.X, Color.Gray);
            }
 
            pbCaptcha.Image = bmp;
        }
    }
}

效果：