Know Captcha

      Net has powerful language features so many people use this language to achieve extremely fast development tasks, and now we are concerned about how to use .Net to generate captcha. In fact, it will generate captcha in several steps, the picture space, draw text, marked with noise, then output image, the process is too simple in .net. The code:

 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;

 namespace SessionCode

{

    public partial class checkimage : System.Web.UI.Page

    {

        protected void Page_Load(object sender, EventArgs e)

        {

            GetCode();

        }

         protected void GetCode()

        {

            System.Random rand = new Random();

            char[] chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();

            System.Text.StringBuilder myStr = new System.Text.StringBuilder();

             for (int iCount = 0; iCount < len; iCount++)

            {

                myStr.Append(chars[rand.Next(chars.Length)]);

            }

            string text = myStr.ToString();

            Size ImageSize = Size.Empty;

              using (Bitmap bmp = new Bitmap(5, 5))

            {

                using (Graphics g = Graphics.FromImage(bmp))

                {

                    SizeF size = g.MeasureString(text, myFont, 10000);

                    ImageSize.Width = (int)size.Width + 3;

                    ImageSize.Height = (int)size.Height + 3;

                }

            }

            using (Bitmap bmp = new Bitmap(ImageSize.Width, ImageSize.Height))

            {

                {

                    g.Clear(Color.White);

                    using (StringFormat f = new StringFormat())

                    {

                        f.Alignment = StringAlignment.Near;

                        f.LineAlignment = StringAlignment.Center;

                        f.FormatFlags = StringFormatFlags.NoWrap;

                        g.DrawString(text, myFont, Brushes.Black, new RectangleF (0, 0, ImageSize.Width, ImageSize.Height), f);

                    }

                }

                int num = ImageSize.Width * ImageSize.Height * 20 / 100;

                for (int iCount = 0; iCount < num; iCount++)

                {

                    int x = rand.Next(ImageSize.Width);

                    int y = rand.Next(ImageSize.Height);

                    int r = rand.Next(255);

                    int g = rand.Next(255);

                    int b = rand.Next(255);

                    Color c = Color.FromArgb(r, g, b);

                    bmp.SetPixel(x, y, c);

                }

                System.IO.MemoryStream ms = new System.IO.MemoryStream();

                bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Png);

                this.Response.ContentType = "image/png";

                ms.WriteTo(this.Response.OutputStream);

                ms.Close();

            }

            myFont.Dispose();

        }

    }

}

       Successful programming language is not without reason, neat and quick to put these things done, you have to say it to be high efficiency, the above code is also very easy to understand, but also a lot of comment. If you have a better code, welcomed the exchange withKnowCaptcha.

     Playing the answer really is not an easy thing, both knowledgeable and fast response, no corresponding knowledge can not answer, it was fast enough to grab someone else, and the most important is the reward so rich that he looked on the heart, someone else took really unwilling. Where can someone help to answer? Perhaps many people ask this question, in fact, KnowCaptcha can help you to do this business.

      KnowCaptcha focus on captcha bypass service and has many years of experience in this area. If you are still not answer the question for yourself, grab the title, no prizes and distress, then came to find KnowCaptcha, which will let you know there is an unexpected harvest.Captcha solver is very mature, and there is professional background device to be directly connected to the client machine, then the topic directly transmitted to the remote answer, do not consume local resources. It has a huge network code exam, and various topics were collecting classified up to answer correctness.

      If you covet those prizes which game they can not afford to do on its own, it is better to find KnowCaptcha to help. As long as moving mouse and waiting, everything is handled automatically, without spending too much effort.

      Where find someone to help? Just here, KnowCaptcha is the best choice, which will make you satisfied, and then want to use again. Welcomg to send e-mail to contact KnowCaptcha.

      Many people want to captcha bypass but they must know what the system will be out of question, they can be prepared in advance, thecaptcha bypass service more quickly than others, if you want to know exactly what the road system that is not specific topic possible because the systems are often designed everything inside the randomness, but if you want to know about what kind of system will be out of question that it still can be done.

      The system will figure out which questions, and your captcha solver level, the history, and the preferences. From the level of speaking, your level is too high, the system naturally will not give you a few simple questions, like the system already knows you‘re a doctor it is no longer give you the title of the pupils, many people do not willing to own high level, it fear to encounter difficulties, so they would rather deliberately answer wrong and stay on the lower level, so you can play it easily. From the historically, the probability you have got wrong in the title repeated higher, this is because the system wants to make you remember these knowledge, so we rely on in this way to strengthen your memory. After a few times you will not forgotten easily. From the preferences, you like to answer what kind of question, you are sure to answer the questions. After several rounds of questions by answering system it can judge them, then it will follow to give out the problems.

      Know about this, you must be very surprised. In fact, the purpose of the question answering system is not to embarrass you, but to make you find a way of entertainment, but also to give you some of the challenges so that you have a sense of captcha human bypass, so the system can predict what will probably be a question of what kind of question is still possible, but you want to know which channel specific problem more difficult, which seems to draw in school teachers will focus on the exam are not directly say what you want to test questions is the same reason.

      The answer has now become an indispensable part of the game, many people have become accustomed to its presence on captcha solver, but the game operators is not so, they should do one thing every reckoning, do some cost analysis, at first for the income, then you make adjustments. Adjust the captcha bypass service for everyone involved, so we still have to be concerned about as well.

      The answer is an integral part of the game, which will have its operational costs yet. First, to increase the cost of that technology to integrate the environment in general and answer game environment, the so-called technology is deployed to increase the manpower or recruitment expert in this area, these will not inevitably appear appropriate to pay, so these costs can not be ignored , of course, but these are more in the early spending, once the environment to build a good future as long as the maintenance on it, late fees will be less. On the other hand, in order to increase the playability of the topic, informative, we must have the appropriate staff collating the corresponding exam, while in the company of such a game is not good to find people, find people with the game and answer probably nothing to do, because it will be relatively large costs are not familiar with. Finally, a new game content, publicity or not, the player should not be adjusted for those which do not, like the money?

      In summary, the game added this need to pay the cost of captcha human bypass, once the effect is not good, operators are likely to put this part of the cut. Now do not worry about our players with this problem? No need, on the current situation, the cost was not as high, the journey is not to charge, in addition to the benefits far outweigh the disadvantages, operators feel quite the value.

   Captcha bypass service into a variety of types, today we mainly come from its recognition to explain in what way the body uses is the best, from the body for identification, captcha bypass service can be divided into local captcha bypass, local captcha bypass and remote captcha bypass combine, remote captcha bypass.

      Local captcha bypass, by definition is received the captcha on the picture of the machine in place to identify. Local captcha bypass if only for personal use, then the effect is quite good, because the captcha image exists on that machine, easy to read directly identify all the work can be carried out in situ, but the disadvantages are also obvious, that is, the speed will be identified and performance-related local machine, good speed on the fast performance, poor performance on slow speed, to consider all the circumstances once the machine-oriented groups, which in practice is very difficult, so to say this approach is not very good. Another way is to identify the combination of local and remote way, this way is to put some complex operations local to the remote machine is running high, although this approach to overcome the differences in speed of recognition performance differences caused by different machines, but because the division of tasks to be carried out, the whole process becomes complicated, it is not too good means of identification. The last is a remote captcha bypass, will be recognized upload pictures to identify the remote high-end machines, and then returns the results from the remote machine, this approach can be easily unified management, but also to constantly adjust structure, is to use a high-level machine or use a cluster can be easily transferred in this way is the best.

      Many sites will always set the Captcha, which is the operator of the site may be a security policy, in the end we do not explore these security policies have no effect, one thing is for sure, and that is ubiquitous Captcha to give Internet users to a poor user experience. Captcha appeared after its rival captcha bypass service also followed emerged Captcha bypass of users which merit it, we come to the following specific analysis.

      Prior said the credit, we have to remind you, there will be certain to use Captcha to identify the shortcomings, someone might use it to carry out his destruction, but everything has two sides, as if technology can harm humans, but can also be for the benefit of mankind, captcha solver has drawbacks, but it is no small credit. The first credit, it allows users activity on the site with more liberty, various Captcha set will deprive you of liberty, and later captcha technology we do not have to wait for it automatically help you fill it. The second credit, which allows Internet users to work more efficiently, and Captcha will undoubtedly seriously affect the speed of things people can not solve problems more smoothly, aftercaptcha solver appears on a nice trip to get things done without any obstacles, efficiency raise a significant role.

      Respondents will answer what kind of psychological change, this issue is very important, because we know that this change in the future will be able to know that there is no captcha solver  to allow players to absorb the knowledge of their habits of mind produced what has changed. Recognizing this problem before and no one has noticed, we now come to studies.

      We start with the aim to analyze it, the captcha bypass service actually has two main purposes, the first is to increase the playability of the game interesting, the game more attractive, which is one pair of game operators, there is a great benefits, and the second is to give players the opportunity to increase their knowledge of the ordinary except for specialized players learn the relevant knowledge, generally are less likely to take the initiative to involve knowledge, because life or work using less, but the expansion of knowledge the richness of a person who is very important to answer so that they can have a chance to force yourself to learn something more. As the players, it is enough to concern the second, we are also major players in research and psychological changes.

      Do captcha bypass service high returns, many people are aware, for the purpose of obtaining more return, many people tried to answer quickly, understand immediately skip, thinking that he definitely can earn more points, it is not true, pay attention to this sort of thing is the quality rather than speed.

      If we observe carefully, then still be able to see some law, that is, the higher the score the more difficult topics, but simple fact, not much of the subject, so if you want by constantly changing the title, to understand their own skip this way to accumulate scores, this method will not work because you are fundamentally no access to a high score of questions, you answer these questions only on the basis of a simple title will appear randomly. The fine art of war, said the soldiers not more expensive, is also used on the right answer, you increase the speed in a short time a lot of questions answered correctly, the number would be much, but it just did, really, if you want to get good grades good reward, more research how best to answer the questions well come on, do not try to jump over through pass approach.

      What is the secret answer is no, there is no shortcut, only let yourself constantly charging, continuous learning in order to obtain good results, this project would have appeared a purpose is to get people to learn and gain knowledge, so I want to get a good ranking on to follow the operator‘s meant to do, for the game, you‘ll have more heart applications for yourself, knowledge has become increasingly diverse, why not!

       I believe everyone on how to build a simple CAPTCHA image are already very familiar with it, but how to generate hard? We just convert simply text into the picture, you also need to add some confusion inside the action, such as twisting, plus interference, mixing, etc., more than just words on captcha bypass service .

 using System;

using System.Collections.Generic;

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Text;

 namespace Smark.ImageNumber

{

    ///

    /// Copyright © henryfan 2012       

    /// Email:  [email protected]   

    /// HomePage:   http://www.ikende.com      

    /// CreateTime: 2012/10/23 21:18:29

    ///

    public class Generator

    {

        const string VALUE = "123456789";

         private static Dictionary mCharImages = new Dictionary(26);

         private static Image mLine;

         private static Random mRam = new Random();

         public static string GeneratorCode()

        {

            string code = "";

            for (int i = 0; i < 4; i++)

            {

                code += VALUE.Substring(GetRamValue() % VALUE.Length, 1);

            }

            return code;

         }

         static int GetRamValue()

        {

             return mRam.Next();

        }

         public static Image GetImage(string code)

        {

            Bitmap tmpImg = new Bitmap(100, 40);

            using (Graphics e = Graphics.FromImage(tmpImg))

            {

                 int offset = 2;

                 e.FillRectangle(new SolidBrush(Color.White), 0, 0, 200, 60);

                 List items = new List();

                foreach (char key in code)

                {

                    items.Add(GetGeneratorItem(key));

                }

                for (int i = 0; i < items.Count; i++)

                {

                    if (i > 0)

                    {

                        if ((items[i].Value < 0 && items[i - 1].Value > 0) || (items[i].Value > 0 && items[i - 1].Value > 0)

                            || (items[i].Value < 0 && items[i - 1].Value < 0))

                            offset += 12;

                         else

                            offset += 18;

                    }

                    using (Image img = items[i].DrawImage())

                    {

                        if (Math.Abs(items[i].Value) > 20)

                            e.DrawImage(img, offset, 6);

                        else if (Math.Abs(items[i].Value) > 20)

                            e.DrawImage(img, offset, 4);

                        else

                            e.DrawImage(img, offset, 2);

                    }

                 }

             }

            return tmpImg;

        }

         public static System.Collections.IEnumerable GetKeys

        {

            get

            {

                return mCharImages.Keys;

            }

        }

         private static GeneratorItem GetGeneratorItem(char key)

        {

            GeneratorItem item = new GeneratorItem();

            int value = GetRamValue() % 25;

            if (value < 10)

                value = 10;

            if (GetRamValue() % 2 == 0)

                value = -value;

            item.Value = value;

            item.Key = key;

            return item;

        }

         class GeneratorItem

        {

            public int Value { get; set; }

            public char Key { get; set; }

            public Image DrawImage()

            {

                Bitmap tmpImg = new Bitmap(50, 50);

                using (Graphics e = Graphics.FromImage(tmpImg))

                {

                    e.RotateTransform(Value, System.Drawing.Drawing2D.MatrixOrder.Append);

                    e.DrawImage(mCharImages[Key], 0, 0);

                    e.Flush();

                }

                return tmpImg;

            }

        }

         static Generator()

        {

             HatchBrush sb = new HatchBrush(HatchStyle.Percent40, Color.Black, Color.Black);

             foreach (char item in VALUE)

            {

                 Bitmap bmp = new Bitmap(50, 50);

                using (Graphics g = Graphics.FromImage(bmp))

                {

                    g.DrawString(new string(new char[] { item }), new Font("宋体", 24, FontStyle.Italic), sb, 2, 2);

                }

                mCharImages[item]= bmp;

            }

             mLine = new Bitmap(60, 4);

            using (Graphics g = Graphics.FromImage(mLine))

            {

                g.FillRectangle(sb, 0, 0, 60, 3);

            }

         }

    }

}

     KnowCaptcha bypass quickly captcha, whether the user is on a vintage machine or on a newbest most recent wave machine, this rate is almost new machine maybe we can understand, why the old the machine can also have such a good effect? 

        I tell you what, in essence, are they and what is the user‘s machine is irrelevant, because captcha bypass service of KnowCaptcha is carried out on a cloud system.

      Cloud system you can think of it as a a computer, a superb computer and all other computers connected to it can command it to do things, there are many  software on this super computers, as well as appropriate organizational methods, you just give it issued a simple command it to do many complex things and give a simple result, so almost all the work  done on the cloud system, of course, and there is not much relationship between the local computer .

      Assign things to do best person to do this, KnowCaptcha follow this code design principles have so much experience, then set up a number of software and systems, of course, does not think the user‘s machine will be comparable to KnowCaptcha, and let KnowCaptcha machine to do the job is the most effective and fast thing, but the fact is true.

      Fear delaying to play the game, which is not just for those adversarial nature of real-time strategy game established for other types of games is also true, for example, the answer is often encountered. Likely to delay any point behind rivals are likely to miss captcha bypass service, which is that people want to see. Many people will get used to using KnowCaptcha to help answer. But why can KnowCaptcha be so smooth?

      KnowCaptcha does not depend on the network user‘s machine, and if he is a master machine will not answer it for a long time, but also talk about what it smooth, currently the biggest feature of this system is independent of the user‘s machine , everyone doing the same questions answered speeds are almost equivalent, but there are differences because the machine will not be much difference. KnowCaptcha has nothing to do with the machine, which comes to the cloud, the cloud system is equivalent to a super machine, all the problems it will be able to answer that one was out, the machine is much faster than the average, and that this is how the super machine with the user‘s machine collaboration yet.

      Cooperative transmission cloud systems and users rely on the network to complete, the user issues commands to execute instructions while cloud systems, such as the user‘s machine says "Preparing the topic" Cloud system is ready to be prepared to answer, "get topic "cloud systems began to accept the user‘s computer to upload to the subject," problem solving "cloud system grunt in question come from the solution, of course, human are unable to feel it in the end to perform a number of actions, but because of a blink it gives the answer.

       Many websites are now doing with php or asp, but there are other sites do with jsp, thanks to the advantages of this website java, and will bring no small advantage, then we should how to use java way to solve captcha bypass service, here is a solution to the captcha solver, we want to help.

import javax.servlet.*;

import javax.servlet.http.*;

import java.io.*;

import java.awt.*;

import java.awt.image.*;

import java.util.*;

import javax.imageio.*;

/**

 * @author  yeeku.H.lee [email protected]

 * @version  1.0

 * Copyright (C), 2005-2008, yeeku.H.Lee

 * This program is protected by copyright laws.

 * Program Name:

 * Date:

 */

public class AuthImg extends HttpServlet

{

    private Font mFont = new Font("Arial Black", Font.PLAIN, 16);

    public void init() throws ServletException

    {

        super.init();

    }

    Color getRandColor(int fc,int bc)

    {

        Random random = new Random();

        if(fc>255) fc=255;

        if(bc>255) bc=255;

        int r=fc+random.nextInt(bc-fc);

        int g=fc+random.nextInt(bc-fc);

        int b=fc+random.nextInt(bc-fc);

        return new Color(r,g,b);

    }

    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException

    {

        response.setHeader("Pragma","No-cache");

        response.setHeader("Cache-Control","no-cache");

        response.setDateHeader("Expires", 0);

        response.setContentType("image/jpeg");

                int width=100, height=18;

        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

                Graphics g = image.getGraphics();

        Random random = new Random();

        g.setColor(getRandColor(200,250));

        g.fillRect(1, 1, width-1, height-1);

        g.setColor(new Color(102,102,102));

        g.drawRect(0, 0, width-1, height-1);

        g.setFont(mFont);

        g.setColor(getRandColor(160,200));

        for (int i=0;i<155;i++)

        {

            int x = random.nextInt(width - 1);

            int y = random.nextInt(height - 1);

            int xl = random.nextInt(6) + 1;

            int yl = random.nextInt(12) + 1;

            g.drawLine(x,y,x + xl,y + yl);

        }

        for (int i = 0;i < 70;i++)

        {

            int x = random.nextInt(width - 1);

            int y = random.nextInt(height - 1);

            int xl = random.nextInt(12) + 1;

            int yl = random.nextInt(6) + 1;

            g.drawLine(x,y,x - xl,y - yl);

        }

        String sRand="";

        for (int i=0;i<6;i++)

        {

   String tmp = getRandomChar();

            sRand += tmp;

            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));

         g.drawString(tmp,15*i+10,15);

        }

        HttpSession session = request.getSession(true);

        session.setAttribute("rand",sRand);

        g.dispose();

        ImageIO.write(image, "JPEG", response.getOutputStream());

    }

    private String getRandomChar()

    {

  int rand = (int)Math.round(Math.random() * 2);

  long itmp = 0;

  char ctmp = ‘u0000‘;

  switch (rand)

  {

   case 1:

    itmp = Math.round(Math.random() * 25 + 65);

    ctmp = (char)itmp;

    return String.valueOf(ctmp);

   case 2:

    itmp = Math.round(Math.random() * 25 + 97);

    ctmp = (char)itmp;

    return String.valueOf(ctmp);

   default :

    itmp = Math.round(Math.random() * 9);

    return String.valueOf(itmp);

  }

    }

}

      This is where the line plus interference, and the use session to save the captcha in the login jsp page, the following function.

      The reason why there is "now", is to prevent the browser cache and finally configure the servlet in the web.xml.

  What are the biggest pleasure is to play the game? When the clearance is that while jumping, is a hot topic invincible hand that happy, that is just the kind of computer abuse joyous, these are the ultimate gaming experience, although many people in the other game environments are more or less and less these states can be achieved, but once the answer to this link, they can always pass the test are also somewhat frustrated state of mind, and perhaps others is brave brave fight to kill Reggie, but let someone else do these files wrinkled wordplay indeed a bit difficult. Everyone wants to experience the ultimate gaming experience, they are not good at it because it has been not to do it? No, KnowCaptcha can do.

      What is KnowCaptcha? It is a platform for captcha solver, having knowledge database, and so on, everyone can think of a term to describe themselves, in fact, what was just a formality, importantly, what it does, what does KnowCaptcha solve all kinds of game players answer appears, allowing you to easily cross the border, not to let the game blow your emotions.

      With the help of KnowCaptcha, each game the player will no longer be trapped in one part fear, and many times the game also can not go to the next level if you do not solver the problem, this is not a difficult one yet, but it does not matter, KnowCaptcha do is to eliminate such a stumbling block. Once the answer appears, the title will be transferred immediately to the background, and then from the cloud to answer, and the answer came back pass, and finally be able to smoothly proceed to the next player off.

      Many people have been looking for the best way to exercise a thought, and is there a way to do this? Before the network developed, it si hard to find another way of thinking of such a workout, but now, with the network, we can use captcha bypass service to connect to numerous exam inside, which is equivalent to the resources that we have almost no unlimited exercise. In many ways, I especially recommend the network to answer.

      The reason to make such a recommendation is mainly based on the following several reasons. The first reason is that it indeed can make your mind can be improved, which means that it is effective. We often comes to efficiency issues, if a method of exercise can not achieve the desired effect, then this method will not get the promotion, nor was extended because of the low efficiency, so the time and effort to be spent on more harm than good . Why answer efficiency is which was caused by the environment, when the answer is not just to face the subject, you have to face the thousands and tens of thousands like you who answer, you have to compete with them, this will not only exercise your ability to acquire knowledge, but also exercise your ability to respond quickly, because you do not pay attention to the words of others before you step on to win the title.

      I recommend the answer because there is another reason, and that is the captcha solver and knowledge will combine together, so you entertaining, learning new knowledge. The more I feel, the more conducive to knowledge absorption, so the thinking exercise has great benefits, the amount of knowledge will get much more than usual.

      Here recommend all my friends pay attention to this point, that is, do not put the answer as a game, although which is being used as part of the game, but it should not conclude that it is a game. When you do not take it as a game, you can get more in captcha bypass service.

      Why should not the answer as a game of it, the reason is very simple, because it make you highly concentrate on the game is to relax you. What is the purpose of the game we play it, and that is after a day of intense relaxation can find some things to do, the nature of the game should be to relax the spirit, but to answer it, why should not the answer in the game to the game attitude towards it, because if you relax you will not match the speed you get someone good ranking, if you relax and you can not concentrate on the content of the subject, also remember the knowledge contained in the subject, and let the players learn the basic knowledge is a goal of this project, and you even have this basic goal to reach and why play it?

      Although the answer exists as part of the game, but the game should not have come to mind for paternity, so to speak, the game is just a platform that exist in the environment that it has, in fact, in addition to the game can also be used as a platform for other environments, such as websites. If you do with the mentality of the game, you will get very little, but if you can focus more on those with the mentality of learning to treat, you will get a lot.

       The answer is really a very interesting project, there are many strong subject knowledge, no expertise, no broad vision simply can not answer these questions, this is the place where so many little fascinated, because it allows you to continue to have learning new knowledge impulse, but if captcha bypass service will answer these questions, and the answers come to many questions can not say that he is educated people, the answer is "Definitely not."

      Why would the answer can not be considered educated people it is very simple, educated people want to express your cultural qualities, skills alone are not any instructions you are educated people: write beautiful calligraphy count? Too! Couplet on the well count? Too! When we say that a person educated, we are saying that the overall quality of his strong words, he was all good, you let him answer, he must Good answer, you let him do the other things he can do better.

      Simply put, educated people are digested into their own, and you do at this level yet. A person‘s knowledge is not enough, then he would not answer those questions, naturally do not have much personal influence, and in turn a person Good answer, it will not be great personal influence it, necessarily, will not answer you must let others convince you. Educated car is not an objective description of things, because there is no one specific thing, it noted that the social evaluation, more and more people believe that you serve the more you can show that you educated people.

       KnowCaptcha wrote how to generate the captcha on the website of the article, today we come to look at how to use asp.net to achieve the goal of generating the captcha, this time, we will verify several code related to the function are put inside, it‘s very easy to use call function can generate a wide variety of images, captcha solver has become much easier.

 public class ValidateCode : System.Web.UI.Page

 {

  private void Page_Load(object sender, System.EventArgs e)

  {

   this.CreateCheckCodeImage(GenerateCheckCode());

  }

  override protected void OnInit(EventArgs e)

  {

   InitializeComponent();

   base.OnInit(e);

  }

  private void InitializeComponent()

  {  

   this.Load += new System.EventHandler(this.Page_Load);

  }

  #endregion

  private string GenerateCheckCode()

  {

   int number;

   char code;

   string checkCode = String.Empty;

    System.Random random = new Random();

    for(int i=0; i<5; i++)

   {

    number = random.Next();

     if(number % 2 == 0)

     code = (char)(‘0‘ + (char)(number % 10));

    else

     code = (char)(‘A‘ + (char)(number % 26));

     checkCode += code.ToString();

   }

    Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

    return checkCode;

  }

   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

   {

     Random random = new Random();

    g.Clear(Color.White);

     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(checkCode, font, brush, 2, 2);

    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()));

    }

    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();

   }

  }

 }

Use the following code to determine Captcha to handle events in the login button in the login page：

   private void btnLogin_Click(object sender, System.Web.UI.ImageClickEventArgs e)

  {

   if(Request.Cookies["CheckCode"] == null)

   {

    lblMessage.Text = "Cookies，";

    lblMessage.Visible = true;

    return;

   }

   if(String.Compare(Request.Cookies["CheckCode"].Value, txtCheckCode.Text, true) != 0)

   {

    lblMessage.Text = "Error Captcha ";

    lblMessage.Visible = true;

    return;

   }

  }