How to set threshold value for Hough Transform

1. What is theta in Hough transform?
2. How does Hough line detection work?
3. Which processing is required to be applied before hough line transform?

What is theta in Hough transform?

The function uses the parametric representation of a line: rho = x*cos(theta) + y*sin(theta) . The function returns rho , the distance from the origin to the line along a vector perpendicular to the line, and theta , the angle in degrees between the x-axis and this vector.

How does Hough line detection work?

If two edge points lay on the same line, their corresponding cosine curves will intersect each other on a specific (ρ, θ) pair. Thus, the Hough Transform algorithm detects lines by finding the (ρ, θ) pairs that have a number of intersections larger than a certain threshold.

Which processing is required to be applied before hough line transform?

Edge detection is often used as preprocessing to Hough preprocessing to Hough transform.