How to Write a Captcha Solver that uses DeathByCaptcha service

Let’s look at a practical example on how to solve CAPTCHAs using the DeathByCaptcha service. This example is written in C#, but you can get it in Java as well.

I use the Web Scraper Testing Ground as an example of a CAPTCHA-protected web page, but I recognize the first  CAPTCHA only as the most difficult one. Also since CAPTCHA images are generated dynamically I use Selenium WebDriver with Firefox to capture them.

If you don’t want to use the DeathByCaptcha service you can substitute it with some OCR software like GSA Capture Breaker. It simulates the service locally, allowing you to not pay per each captcha recognition.

I want to start explaining the code portion by portion, but if you don’t have time to read all the explanations you can find the complete code at the end of the post or download a ready project here.

OK, let’s start!

First, we need to initialize the WebDriver and open the target webpage with captcha:

using (var driver = new FirefoxDriver())
{
    driver.Navigate().GoToUrl("http://testing-ground.scraping.pro/captcha");

Then we need to obtain the CAPTCHA image. Since the WebDriver doesn’t allow us to explicitly extract dynamically created images from the page, let’s create a screenshot of the whole page and then crop the captcha image basing on image position on the web page:

var arrScreen = driver.GetScreenshot().AsByteArray;
using (var msScreen = new MemoryStream(arrScreen))
{
    var bmpScreen = new Bitmap(msScreen);
    var cap = driver.FindElementById("captcha");
    var rcCrop = new Rectangle (cap.Location, cap.Size);
    Image imgCap = bmpScreen.Clone(rcCrop, bmpScr.PixelFormat);

Now, since we have the CAPTCHA image, we can send it to the DeathByCaptcha service for further recognition:

using (var msCaptcha = new MemoryStream())
{
    imgCap.Save(msCaptcha, ImageFormat.Png);
    // put your DeathByCaptcha credentials here
    var client = new SocketClient("user", "password");
    var res = client.Decode(msCaptcha.GetBuffer(), 20);

After we receive a response from the service and the captcha is recognized, we can type its code into the textbox and click the “submit” button:

if (res!=null && res.Solved && res.Correct)
{
    driver.FindElementByXPath("//input[@name='captcha_code']")
    .SendKeys(res.Text);

    driver.FindElementByXPath("//input[@name='submit']")
    .Click ();

Then after the page reloads we can check whether the server accepted our captcha or not. If the captcha was recognized incorrectly, we need to send this report back to the DeathByCaptcha service:

var h4 = driver.FindElementByXPath("//div[@id='case_captcha']//h4");
if (!h4.Text.Contains("SUCCESSFULLY"))
{
    Console.WriteLine("The captcha has been solved incorrectly!");
    client.Report(res);
}
else
    Console.WriteLine("The captcha has been solved correctly!");

That’s it! Here is the complete code of the application:

using System;
using System.Drawing;
using System.Drawing.Imaging;
using OpenQA.Selenium.Firefox;
using DeathByCaptcha;
using System.IO;

namespace CaptchaSolver
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Initializing the Firefox webdriver...");
            using (var driver = new FirefoxDriver())
            {
                Console.WriteLine("Opening the page...");
                driver.Navigate().GoToUrl("http://testing-ground.scraping.pro/captcha");

                var arrScreen = driver.GetScreenshot().AsByteArray;
                using (var msScreen = new MemoryStream(arrScreen))
                {
                    var bmpScreen = new Bitmap(msScreen);
                    var cap = driver.FindElementById("captcha");
                    var rcCrop = new Rectangle (cap.Location, cap.Size);
                    Image imgCap = bmpScreen.Clone(rcCrop, bmpScreen.PixelFormat);

                    using (var msCaptcha = new MemoryStream())
                    {
                        imgCap.Save(msCaptcha, ImageFormat.Png);

                        // put your DeathByCaptcha credentials here
                        var client = new SocketClient("user", "password");

                        Console.WriteLine("Sending request to DeathByCaptcha...");
                        var res = client.Decode(msCaptcha.GetBuffer(), 20);
                        if (res!=null && res.Solved && res.Correct)
                        {
                            driver.FindElementByXPath ( "//input[@name='captcha_code']" ).SendKeys(res.Text);

                            driver.FindElementByXPath ( "//input[@name='submit']" ).Click ();

                            var h4 = driver.FindElementByXPath("//div[@id='case_captcha']//h4");
                            if (!h4.Text.Contains("SUCCESSFULLY"))
                            {
                                Console.WriteLine("The captcha has been solved incorrectly!");
                                client.Report(res);
                            }
                            else
                                Console.WriteLine("The captcha has been solved correctly!");
                        }
                        else
                            Console.WriteLine("Captcha recognition error occured");
                    }
                }
            }
            Console.ReadKey();
        }
    }
}

Don’t forget that you can  download the complete VS Project. And feel free to ask any questions or give any responses!