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：
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<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：
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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 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(); } }} |
以上就是关于asp.net生成图形验证码的相关资料，希望对大家的学习有所帮助。
