Hough transform line follower

Question

Okay, I want to make a program to detect a line from a camera stream. This is for al line follower robot. So if the robot know the angle of two parallel lines, he knew in which way he must ride.

I perform the follow functions:

• Make frame gray
• Gaussian blur
• Canny edge
• Hough transform

The first thing is, that when there are no lines, the program is terminated. (also when there are only a few lines).

I don't know how to solve that.

Also, I want to get the angle of the line(s). And I want to get the distance of 2 parallel lines (and know witch 2 lines are parallel)

Here is my very simple code, i contains most of the examples on the internet:

import numpy as np
import cv2

cap = cv2.VideoCapture(0)
ret = cap.set(3,640)
ret = cap.set(4,480)

while True:
ret, frame = cap.read()
gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)
gauss = cv2.GaussianBlur(gray,(3,3),0)
edges = cv2.Canny(gray,0,150,apertureSize = 3)
lines = cv2.HoughLines(edges,1,np.pi/180,50)

for rho,theta in lines[0]:
    a = np.cos(theta)
    b = np.sin(theta)
    x0 = a*rho
    y0 = b*rho
    x1 = int(x0 + 1000*(-b))
    y1 = int(y0 + 1000*(a))
    x2 = int(x0 - 1000*(-b))
    y2 = int(y0 - 1000*(a))
    cv2.line(frame,(x1,y1),(x2,y2),(0,0,255),2)

cv2.imshow('frame',edges)
cv2.imshow('frame',frame)

Answer 1

maybe 'try' can solve that:

while True:
    try:
      'your code'
    except:
      'other code'

this way an error wouldn't end the program, but you could decide what to do.