132 karma · joined January 19, 2013
OK, I didn't write the JPEG decoder, but how far do you want me to go?!
RGB to grayscale: V = r x g x b/3 (one line).
The Sobel operation is at most 4 nested loops (really only 3) for a total of ~7 lines of code, depending on how you like your white space.
Fold the summation into your Sobel function without requiring another line.
The most complicated thing used from the OpenCV library (which I'm well aware is C++!) is JPEG decoding. OK, I'm avoiding swirling, but then it isn't needed to solve the CAPTCHA anyway.
> If you had to write the un-swirling, gray-scaling, Sobel filtering and summation code in Python you'd be looking at a much larger pile-o-code
I would also like to point out these are also all very simple operations, which would only take a few lines of Python/C/whatever to do. Python just happens to have a pre-written libraries to save reinventing the wheel.