OpenCV HoughLinesP threshold parameter

0
votes

C++: void HoughLinesP(InputArray image, OutputArray lines, double rho, double theta, int threshold, double minLineLength=0, double maxLineGap=0 )

I have difficulties understanding the parameter in below. Could some explain it like one would for dummies type thing?.

threshold – Accumulator threshold parameter. Only those lines are returned that get enough votes ( >\texttt{threshold} ).
1
opencvopencv3.0

1 Answers

0
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Seems you have not understood the Hough Algorithm. I hope a intro or short description on hough line detection algo below will surely help you. Ref: Wiki,Tutorial.

  1. Consider a edge (sobel or canny's output) image.
  2. For each edge point (Xi,Yi) in the image calculate: Pi = XicosT+YiSinT
  3. Increment the accumulator at A(Pi,T) = A(Pi,T) + 1.

where, Pi - Distance and T (theta) - Angle. Theta ranges from 0-360. A(Pi,T) is referred as hough space. By finding the accumulator bins with the highest values, typically by looking for local maxima in the accumulator space, the most likely lines can be extracted. Usually finding highest values are done by a parameter threshold.

Try changing the threshold values, you will find significant change in the line detection.