[chad1n]

I've built 3 iterations of captcha solvers for that crappy website based on https://github.com/drunohazarb/4chan-captcha-solver/issues/1 . The only thing I've learned along the way is that it's mostly pointless outside of a "learning" exercise, since they'll change the captcha (in terms of letter count or the entropy background). Initially, it was 4 characters with pretty obvious background, then it turned to 5, then it was both 4 and 5 and the current iteration which is also either 4 or 5, but with a lot of entropy surrounding the characters.

[blackjackfoe]

This project was really my first decent introduction to computer vision and machine learning (along with that of those who helped me in various ways; none of them desired to be credited here other than the guy who collected some of the data for me.)

It was definitely a successful learning exercise, and it's made me more confident tackling some other problems I've had in mind for awhile.

[spookie]

To help you out if you're interested:

- a smeared gaussian in one axis and another in another axis can really help segmenting chars, finding lines of text in OCR

- You can unshear chars using the Radon or Hough transform as a basis to understand the angle

Went through MNIST a few weeks ago and I agree it's interesting!

[blackjackfoe]

I am always interested! Thank you for the tips, I'll definitely research these.

[sorenjan]

Shearing is a linear operation that should be trivial for a NN to learn. Have you found that unshearing is actually useful? Was it to feed the image to an existing OCR program?

[normie3000]

How did this project help you to learn computer vision? I'd also like to write a basic captcha solver as an intro, but superficially this project just looks like a dump of generated code.

[blackjackfoe]

What do you mean by "generated code"? All of the code in the linked GitHub repo was written by me, with the assistance of a couple friends who helped here and there, but didn't request to be credited.

I learned a lot because I had to do a ton of research and experimentation (fancy word for trial-and-error) to write the code and have it work as I expected.

[normie3000]

I think there's been a misunderstanding. I didn't understand you were the author of the linked article, and read the following exchange to mean you'd found the code at https://github.com/drunohazarb/4chan-captcha-solver to be a helpful introduction:

> > I've built 3 iterations of captcha solvers for that crappy website based on https://github.com/drunohazarb/4chan-captcha-solver/issues/1

> This project was really my first decent introduction to computer vision and machine learning

I see now that your code is linked from the article, and looks really informative - thanks for sharing!

[bryan0]

In the article it mentions they changed the number of characters in the captcha after he trained the model, and the model could still solve it

[oefrha]

Changing the number of characters barely registers as a change. They merely need to use a variety of fonts (according to the post right now there are a grand total of 15 possible glyphs which is tiny) and it would vastly increase the difficulty of generating the training set, and probably affect model accuracy by a lot. Not to mention more complex backgrounds. What’s seen here is an ancient and relatively simple form of captcha.