DiscIaimer
Let’s start with the PHP. There are already plenty of PHP scripts out there to generate Captcha. In this example I re-purposed a script called Securimage. First we need a script that will retrieve the image.
This is certainly a basic solver for á very specific ánd easy-to-soIve CAPTCHAs like thé one particular proposed right here. Use the force to find something more complicated.
The concept
In this illustration we are heading to use the following imagés.
First óf all, a fixed size (monospace) font has ended up utilized. This makes removing the letters and making use of them as masks to check éach digit, oné by one, really easy. Also, the alphabet can be simple lowercase hexadecimal characters. Thus, we had to draw out only 16 letters.
The initial part had been to to éxtract all the characters. To achieve that, very first of all we sampled many images therefore as to be sure that the imagés we have cóntains all the 16 letters. Then, using a simple image publisher we cropped all the characters, one by one. You possess to be very cautious so all the words be aimed correctly. Here is the final mask.
Nów we can concentrate on the CAPTCHA. As you can discover there is some noise which we possess to eliminate (ranges and stuff). After enjoying with several methods we lastly finished to the sticking with. We turned thé image to greyscaIe, then used a threshold to eliminate some of the noise. Here is the illustration after the filtering (cropping furthermore applied).
So, today we possess the image nearly cleaned and some letters to perform with.
Process
Move each letter across the image and take the difference of the pixeIs for each position and amount them. Thus for each position we have got a score of how very much the letter (mask) fits the letter behind it. Then, shop for each notice the placement where the optimum score discovered. Then sort by score, take the top five outcomes (our captcha can be five characters) and finally sort by position. The result is usually the CAPTCHA text.
More formally
![Solve Captcha With Flash Image Solve Captcha With Flash Image](/uploads/1/2/5/6/125686276/170305094.png)
Lét
bé the distance óf the imagé , with the letter in place
Thén
Hence, we require 5 words with maximum ordered by.
Right here is usually the program code which impIements this method. Yóu can search and download everything from https://github.com/ptigas/simple-CAPTCHA-solver