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理解C#生成验证码的过程

︶ㄣ速达网 メ
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这篇文章主要介绍了C#生成验证码的过程，通过实例分析C#验证码的生成原理，感兴趣的小伙伴们可以参考一下

本文实例为大家介绍了生成验证码的详细过程，供大家参考，具体内容如下

生成验证码的类：

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using System;
using System.Collections.Generic;
using System.Drawing;
using System.Text;
 
namespace Controllers.Core.Util
{
  /// <summary>
  /// 验证码
  /// </summary>
  public class VerifyCodeHelper : AdminBaseController
  {
    #region 变量
    /// <summary>
    /// 颜色表
    /// </summary>
    private static Color[] colors = new Color[]{
      Color.FromArgb(220,20,60),
      Color.FromArgb(128,0,128),
      Color.FromArgb(65,105,225),
      Color.FromArgb(70,130,180),
      Color.FromArgb(46,139,87),
      Color.FromArgb(184,134,11),
      Color.FromArgb(255,140,0),
      Color.FromArgb(139,69,19),
      Color.FromArgb(0,191,255),
      Color.FromArgb(95,158,160),
      Color.FromArgb(255,20,147),
      Color.FromArgb(255,165,0)};
 
    /// <summary>
    /// 字体表
    /// </summary>
    private static string[] fonts = new string[] {
      "Arial",
      "Verdana",
      "Georgia",
      "黑体" };
 
    /// <summary>
    /// 字体大小
    /// </summary>
    private static int fontSize = 22;
    #endregion
 
    #region 生成验证码图片
    /// <summary>
    /// 生成验证码图片
    /// </summary>
    public static Bitmap CreateVerifyCodeBmp(out string code)
    {
      int width = 120;
      int height = 40;
      Bitmap bmp = new Bitmap(width, height);
      Graphics g = Graphics.FromImage(bmp);
      Random rnd = new Random();
 
      //背景色
      g.FillRectangle(new SolidBrush(Color.White), new Rectangle(0, 0, width, height));
 
      //文字
      StringBuilder sbCode = new StringBuilder();
      for (int i = 0; i < 4; i++)
      {
        string str = GetChar(rnd);
        Font font = GetFont(rnd);
        Color color = GetColor(rnd);
        g.DrawString(str, font, new SolidBrush(color), new PointF((float)(i * width / 4.0), 0));
        sbCode.Append(str);
      }
      code = sbCode.ToString();
 
      //噪音线
      for (int i = 0; i < 10; i++)
      {
        int x1 = rnd.Next(bmp.Width);
        int x2 = rnd.Next(bmp.Width);
        int y1 = rnd.Next(bmp.Height);
        int y2 = rnd.Next(bmp.Height);
 
        Pen p = new Pen(GetColor(rnd), 1);
        g.DrawLine(p, x1, y1, x2, y2);
      }
 
      //扭曲
      bmp = TwistImage(bmp, true, 3, rnd.NextDouble() * Math.PI * 2);
      g = Graphics.FromImage(bmp);
 
      //噪点
      for (int i = 0; i < 100; i++)
      {
        int x1 = rnd.Next(bmp.Width);
        int y1 = rnd.Next(bmp.Height);
 
        Pen p = new Pen(GetColor(rnd), 1);
        g.DrawRectangle(p, x1, y1, 1, 1);
      }
 
      //边框
      g.DrawRectangle(new Pen(new SolidBrush(Color.FromArgb(153, 153, 153))), new Rectangle(0, 0, width - 1, height - 1));
 
      return bmp;
    }
    #endregion
 
    #region 获取随机字符
    /// <summary>
    /// 获取随机字符
    /// </summary>
    private static string GetChar(Random rnd)
    {
      int n = rnd.Next(0, 61);
      if (n <= 9)
      {
        return ((char)(48 + n)).ToString();
      }
      else if (n <= 35)
      {
        return ((char)(65 + n - 10)).ToString();
      }
      else
      {
        return ((char)(97 + n - 36)).ToString();
      }
    }
    #endregion
 
    #region 获取随机字体
    /// <summary>
    /// 获取随机字体
    /// </summary>
    private static Font GetFont(Random rnd)
    {
      return new Font(fonts[rnd.Next(0, fonts.Length)], fontSize, FontStyle.Bold);
    }
    #endregion
 
    #region 获取随机颜色
    /// <summary>
    /// 获取随机颜色
    /// </summary>
    private static Color GetColor(Random rnd)
    {
      return colors[rnd.Next(0, colors.Length)];
    }
    #endregion
 
    #region 正弦曲线Wave扭曲图片
    /// <summary> 
    /// 正弦曲线Wave扭曲图片（Edit By 51aspx.com） 
    /// </summary> 
    /// <param name="srcBmp">图片路径</param> 
    /// <param name="bXDir">如果扭曲则选择为True</param> 
    /// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高，一般为3</param> 
    /// <param name="dPhase">波形的起始相位，取值区间[0-2*PI)</param> 
    private static System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
    {
      System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
 
      // 将位图背景填充为白色 
      System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);
      graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
      graph.Dispose();
 
      double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;
 
      for (int i = 0; i < destBmp.Width; i++)
      {
        for (int j = 0; j < destBmp.Height; j++)
        {
          double dx = 0;
          dx = bXDir ? (Math.PI * 2 * (double)j) / dBaseAxisLen : (Math.PI * 2 * (double)i) / dBaseAxisLen;
          dx += dPhase;
          double dy = Math.Sin(dx);
 
          // 取得当前点的颜色 
          int nOldX = 0, nOldY = 0;
          nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
          nOldY = bXDir ? j : j + (int)(dy * dMultValue);
 
          System.Drawing.Color color = srcBmp.GetPixel(i, j);
          if (nOldX >= 0 && nOldX < destBmp.Width
           && nOldY >= 0 && nOldY < destBmp.Height)
          {
            destBmp.SetPixel(nOldX, nOldY, color);
          }
        }
      }
 
      return destBmp;
    }
    #endregion
 
  }
}

验证码页面Action：

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public ActionResult VerifyCode()
{
  string code;
  Bitmap bmp = VerifyCodeHelper.CreateVerifyCodeBmp(out code);
  Bitmap newbmp = new Bitmap(bmp, 108, 36);
  HttpContext.Session["VerifyCode"] = code;
 
  Response.Clear();
  Response.ContentType = "image/bmp";
  newbmp.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Bmp);
 
  return View();
}

说明：前台页面为空的cshtml页面，验证码的值放在Session中。

使用验证码的页面：

显示验证码的img：

<img id="verifyCode" src="" csharp" id="highlighter_976932">

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$(function () {
  //刷新验证码
  $("#refreshVerifyCode").click(function () {
    refreshVerifyCode(); //刷新验证码
  });
  $("#verifyCode").click(function () {
    refreshVerifyCode(); //刷新验证码
  });
  refreshVerifyCode();
});