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

That's interesting about the theta being the angle between the line and the y-axis.

Generally, the rho and theta values are visualized as being the angle from the x-axis to the line perpendicular to the line in question. The rho is then the length of this perpendicular line. Thus, a theta = 90 and rho = 20 would mean a horizontal line 20 pixels up from the origin. A nice image is shown on Hough Transform question