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