How to test proximity of lines (Hough transform) in OpenCV

Question

(This is a follow-up from this previous question).

I was able to successfully use OpenCV / Hough transforms to detect lines in pictures (scanned text); at first it would

Answer 1

If you use the standard or multiscale hough, you will end up with the rho and theta coordinates of the lines in polar coordinates. Rho is the distance to the origin, and theta is normally the angle between the detected line and the Y axis. Without looking into the details of the hough transform in opencv, this is a general rule in those coordinates: two lines will be almost parallel and very near one another when: - their thetas are nearly identical AND their rhos are nearly identical OR - their thetas are near 180 degrees apart AND their rhos are near each other's negative

I hope that makes sense.