using System;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;

namespace BLL
{
    public class Captcha
    {
        public static byte[] GenerateCaptcha(out string captchaText)
        {
            Random random = new Random();
            //StringBuilder sb = new StringBuilder();
            // 生成4位随机数字作为验证码
            //for (int i = 0; i < 4; i++)
            //{
            //    sb.Append(random.Next(0, 9));
            //}
            //captchaText = sb.ToString();

            const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
            captchaText = new string(Enumerable.Repeat(chars, 4)
                                                  .Select(s => s[random.Next(s.Length)]).ToArray());

            using (Bitmap bitmap = new Bitmap(100, 30))
            {
                using (Graphics g = Graphics.FromImage(bitmap))
                {
                    g.Clear(Color.White);

                    // 绘制边框
                    g.DrawRectangle(new Pen(Color.Black), 0, 0, bitmap.Width - 1, bitmap.Height - 1);

                    // 绘制验证码
                    Font font = new Font("Arial", 15, FontStyle.Bold);
                    g.DrawString(captchaText, font, Brushes.Black, 5, 5);

                    // 添加噪声线
                    for (int i = 0; i < 10; i++)
                    {
                        Point start = new Point(random.Next(bitmap.Width), random.Next(bitmap.Height));
                        Point end = new Point(random.Next(bitmap.Width), random.Next(bitmap.Height));
                        g.DrawLine(new Pen(Color.Black), start, end);
                    }

                    // 保存图片到内存流
                    using (MemoryStream memoryStream = new MemoryStream())
                    {
                        bitmap.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Png);
                        return memoryStream.ToArray();
                    }
                }
            }
        }
    }
}