Hough transform algorithm
Typically use a different parameterization
d is the perpendicular distance from the line to the origin
is the angle this perpendicular makes with the x axis
Why?
Basic Hough transform algorithm
1. Initialize H[d, ]=0
2. for each edge point I[x,y] in the image
    for = 0 to 180
    H[d, ] += 1
3. Find the value(s) of (d, ) where H[d, ] is maximum
4. The detected line in the image is given by
What’s the running time (measured in # votes)?
Hough line demo