把旧系统迁移到.Net Core 2.0 日记 (13) --图形验证码

参考这篇文章: http://www.cnblogs.com/yuangang/p/6000460.html

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(, Int32.MaxValue - length * );
            int[] seeks = new int[length];
            for (int i = ; i < length; i++)
            {
                beginSeek += ;
                seeks[i] = beginSeek;
            }
            //生成随机数字
            for (int i = ; i < length; i++)
            {
                Random rand = new Random(seeks[i]);
                int pownum =  * (int)Math.Pow(, length);
                randMembers[i] = rand.Next(pownum, Int32.MaxValue);
            }
            //抽取随机数字
            for (int i = ; i < length; i++)
            {
                string numStr = randMembers[i].ToString();
                int numLength = numStr.Length;
                Random rand = new Random();
                int numPosition = rand.Next(, numLength - );
                validateNums[i] = Int32.Parse(numStr.Substring(numPosition, ));
            }
            //生成验证码
            for (int i = ; 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 * , );

            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 = ; i < ; i++)
            {
                int x = random.Next(Img.Width);
                int y = random.Next(Img.Height);
                g.DrawRectangle(new Pen(Color.LightGray, ), x, y, , );
            }
            //验证码绘制在g中
            for (int i = ; i < validateNum.Length; i++)
            {
                int cindex = random.Next();//随机颜色索引值
                int findex = random.Next();//随机字体索引值
                Font f = new Font(fonts[findex], , FontStyle.Bold);//字体
                Brush b = new SolidBrush(c[cindex]);//颜色
                int ii = ;
                if ((i + ) %  == )//控制验证码不在同一高度
                {
                    ii = ;
                }
                g.DrawString(validateNum.Substring(i, ), f, b,  + (i * ), 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();
        }
    }

}

调用方法, Controller加一个方法, HTML里 <img id="cc_image" src="/product/ValidateCode" alt="点击切换验证码">

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

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