把旧系统迁移到.Net Core 2.0 日记 (13) --图形验证码

using System;
using System.IO;
using System.DrawingCore;
using System.DrawingCore.Imaging;

namespace MobileWeb.Utility
{
    public class Captcha
    {

        public string CreateValidateNumber(int length)
        {
            int[] randMembers = new int[length];
            int[] validateNums = new int[length];
            System.Text.StringBuilder validateNumberStr = new System.Text.StringBuilder();
            //生成起始序列值
            int seekSeek = unchecked((int)DateTime.Now.Ticks);
            Random seekRand = new Random(seekSeek);
            int beginSeek = (int)seekRand.Next(0, Int32.MaxValue - length * 10000);
            int[] seeks = new int[length];
            for (int i = 0; i < length; i++)
            {
                beginSeek += 10000;
                seeks[i] = beginSeek;
            }
            //生成随机数字
            for (int i = 0; i < length; i++)
            {
                Random rand = new Random(seeks[i]);
                int pownum = 1 * (int)Math.Pow(10, length);
                randMembers[i] = rand.Next(pownum, Int32.MaxValue);
            }
            //抽取随机数字
            for (int i = 0; i < length; i++)
            {
                string numStr = randMembers[i].ToString();
                int numLength = numStr.Length;
                Random rand = new Random();
                int numPosition = rand.Next(0, numLength - 1);
                validateNums[i] = Int32.Parse(numStr.Substring(numPosition, 1));
            }
            //生成验证码
            for (int i = 0; i < length; i++)
            {
                validateNumberStr.Append(validateNums[i].ToString());
            }
            return validateNumberStr.ToString();
        }

        public byte[] CreateValidateGraphic(string validateNum)
        {
            Bitmap Img = null;
            Graphics g = null;
            MemoryStream ms = null;
            Random random = new Random();
            //验证码颜色集合  
            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };

            //验证码字体集合
            string[] fonts = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };


            //定义图像的大小，生成图像的实例  
            Img = new Bitmap((int)validateNum.Length * 18, 32);

            g = Graphics.FromImage(Img);//从Img对象生成新的Graphics对象    

            g.Clear(Color.White);//背景设为白色  

            //在随机位置画背景点  
            for (int i = 0; i < 100; i++)
            {
                int x = random.Next(Img.Width);
                int y = random.Next(Img.Height);
                g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
            }
            //验证码绘制在g中  
            for (int i = 0; i < validateNum.Length; i++)
            {
                int cindex = random.Next(7);//随机颜色索引值  
                int findex = random.Next(5);//随机字体索引值  
                Font f = new Font(fonts[findex], 15, FontStyle.Bold);//字体  
                Brush b = new SolidBrush(c[cindex]);//颜色  
                int ii = 4;
                if ((i + 1) % 2 == 0)//控制验证码不在同一高度  
                {
                    ii = 2;
                }
                g.DrawString(validateNum.Substring(i, 1), f, b, 3 + (i * 12), ii);//绘制一个验证字符  
            }
            ms = new MemoryStream();//生成内存流对象  
            Img.Save(ms, ImageFormat.Jpeg);//将此图像以Png图像文件的格式保存到流中  

            //回收资源  
            g.Dispose();
            Img.Dispose();
            return ms.ToArray();
        }
    }

}

        public ActionResult ValidateCode()
        {
            Captcha captcha = new Captcha();

            var code = captcha.CreateValidateNumber(4);
            HttpContext.Session.SetString("ValidateCode", code);
            return File(captcha.CreateValidateGraphic(code), "image/jpeg");
        }