乘风原创程序

  • asp.net生成字母和数字混合图形验证码
  • 2020/5/27 16:16:38
  • 验证码技术是网站开发过程中比较重要的技术,可以防止非法人员利用注册机或者登陆工具来攻击我们的网站。下面是效果图:

    具体实现方法如下:

    1、主要思路是:引用Using System.Drawing命名空间,利用Graphics的FromImage方法创建一个画布,同时设置画布的宽和高,然后通过Graphics类 的DrawString方法随机生成的字符串绘制到画布中,绘制验证码的同时,在画布中利用SetPixel方法绘制一些色点,从而防止非法人员利用机器 人来进行登陆。当我们绘制验证码完毕后,在需要验证码的页面中利用Image空间将其显示出来,Image控件显示验证码的HTML源码设置如下:

    <asp:Image ID="Image1" runat="server"ImageUrl="~/ValidateNum.aspx" />
    <asp:LinkButton ID="LinkButton1" runat="server" style="font-size: small; ">看不清,换一张</asp:LinkButton>
    

    2、这里所用到的ValidateNum.aspx页面代码如下:

    using System;
    using System.Collections;
    using System.Configuration;
    using System.Data;
    using System.Linq;
    using System.Web;
    using System.Web.Security;
    using System.Web.UI;
    using System.Web.UI.HtmlControls;
    using System.Web.UI.WebControls;
    using System.Web.UI.WebControls.WebParts;
    using System.Xml.Linq;
    using System.Drawing;
    
    public partial class ValidateNum : System.Web.UI.Page
    {
     protected void Page_Load(object sender, EventArgs e)
     {
      if (!IsPostBack)
      {
       string validateNum = CreateRandomNum(4);//成生4位随机字符串
       CreateImage(validateNum);//将生成的随机字符串绘成图片
       Session["ValidateNum"] = validateNum;//保存验证码
      }
     }
     //生成随机字符串
     private string CreateRandomNum(int NumCount)
     {
      string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
      string[] allCharArray = allChar.Split(',');//拆分成数组
      string randomNum = "";
      int temp = -1;//记录上次随机数的数值,尽量避免产生几个相同的随机数
    
      Random rand = new Random();
      for (int i = 0; i < NumCount; i++)
      {
       if (temp != -1)
       {
        rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
       }
       int t = rand.Next(35);
       if (temp == t)
       {
        return CreateRandomNum(NumCount);
       }
       temp = t;
       randomNum += allCharArray[t];
      }
      return randomNum;
     }
     //生成图片
     private void CreateImage(string validateNum)
     {
      if (validateNum == null || validateNum.Trim() == String.Empty)
       return;
      //生成Bitmap图像
      System.Drawing.Bitmap image = new System.Drawing.Bitmap(validateNum.Length * 12 + 10, 22);
      Graphics g = Graphics.FromImage(image);
    
      try
      {
       //生成随机生成器 
       Random random = new Random();
    
       //清空图片背景色 
       g.Clear(Color.White);
    
       //画图片的背景噪音线 
       for (int i = 0; i < 25; i++)
       {
        int x1 = random.Next(image.Width);
        int x2 = random.Next(image.Width);
        int y1 = random.Next(image.Height);
        int y2 = random.Next(image.Height);
    
        g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
       }
    
       Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
       System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
       g.DrawString(validateNum, font, brush, 2, 2);
    
       //画图片的前景噪音点 
       for (int i = 0; i < 100; i++)
       {
        int x = random.Next(image.Width);
        int y = random.Next(image.Height);
    
        image.SetPixel(x, y, Color.FromArgb(random.Next()));
       }
    
       //画图片的边框线 
       g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
    
       System.IO.MemoryStream ms = new System.IO.MemoryStream();
       //将图像保存到指定的流
       image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
       Response.ClearContent();
       Response.ContentType = "image/Gif";
       Response.BinaryWrite(ms.ToArray());
      }
      finally
      {
       g.Dispose();
       image.Dispose();
      }
     }
    }