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The author:(作者)qqpublished in(发表于) 2014/7/11 9:29:22 GDI+绘制验证码图片
GDI+绘制验证码图片
绘制验证码图片在网站开发过程中,验证码技术是保护网站安全的最基本环节,它可以防止非法人员利用注册工具或登录工具来攻击网站。本节通过一个实例来介绍如何在网站中绘制验证码图片。实例运行结果如图1所示。图1 验证码图片程序开发步骤如下所示:(1)新建一个网站,将其命名为26_04,默认主页名为Default.aspx。(2)在该网站中添加一个code.aspx页面,用于生成验证码图片。(3)程序主要代码如下。code.aspx页面中定义了两个方法,分别为GenerateCheckCode方法和CreateCheckCodeImage方法,其中GenerateCheckCode方法用来生成随机字符串,而CreateCheckCodeImage方法则用来将随机生成的字符串转换成验证码图片。GenerateCheckCode方法实现代码如下:protected string GenerateCheckCode(int number){string checkCode = String.Empty;string Vchar = "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,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O, P,Q,R,S,T,U,V,W,X,Y,Z";string[] VcArray = Vchar.Split(',');int temp = -1; //记录上次随机数值,尽量避免生产几个一样的随机数Random rand = new Random();for (int i = 1; i < number+1; i++){if (temp != -1){rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));}int t = rand.Next(VcArray.Length);if (temp != -1 && temp = = t){return GenerateCheckCode(number);}temp = t;checkCode += VcArray[t];}Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));return checkCode;}CreateCheckCodeImage方法实现代码如下:private void CreateCheckCodeImage(string checkCode){if (checkCode == null || checkCode.Trim() == String.Empty)return;System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 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 < 2; 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.Black), x1, y1, x2, y2);}Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.Font Style.Italic));System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradient Brush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, True);g.DrawString(checkCode, 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();image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);Response.ClearContent();Response.ContentType = "image/Gif";Response.BinaryWrite(ms.ToArray());}finally{g.Dispose();image.Dispose();}}将Default.aspx页设置为首页,在该页中添加一个Image控件,用来显示验证码图片,并将其ImageUrl属性设置为“code.aspx”,实现代码如下:完整程序代码如下:★ ★★★★code.aspx页面设计文件完整程序代码★★★★★<%@ Page Language="C#" AutoEventWireup="true" CodeFile="code.aspx.cs" Inherits="code" %>
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