houghLineEngine.py

# import the necessary packages
import time
import cv2
import numpy as np

def computeLinesFromGRAY(inputImg, edgeThreshold, houghP = True, scale = 1, delta = 0): 


	ddepth = cv2.CV_64F

	# Need to check that the image is indeed a color image. 
	image = cv2.cvtColor(inputImg, cv2.COLOR_BGR2GRAY)

	# Process the optical flow from old_image to image 
	grad_x = cv2.Sobel(image, ddepth, 1, 0, ksize=3, scale=scale, delta=delta, borderType=cv2.BORDER_DEFAULT)
	grad_y = cv2.Sobel(image, ddepth, 0, 1, ksize=3, scale=scale, delta=delta, borderType=cv2.BORDER_DEFAULT)

	# Display the optical flow 
	pop_pop, angles = cv2.cartToPolar(grad_x, grad_y) # It's called pop_pop because "pop pop is magnitude" 
	toDisplay = cv2.cvtColor(pop_pop.astype('uint8'), cv2.COLOR_GRAY2BGR)
	# edgeImg = np.min(pop_pop, edgeThreshold)
	edgeImg = np.zeros(pop_pop.shape, dtype=float)
	edgeImg[pop_pop >= edgeThreshold] = 255.0

	
	if houghP: 
		lines = cv2.HoughLinesP(edgeImg.astype('uint8'), 1, np.pi / 180, 50, None, 50, 10) # Corresponds to 
		if lines is not None: 
			for oneLine in range(0,len(lines)): 
				currentLine = lines[oneLine][0]
				cv2.line(toDisplay, (currentLine[0], currentLine[1]), (currentLine[2], currentLine[3]), (0,0,255), 3, cv2.LINE_AA)

	else: 
		lines = cv2.HoughLines(edgeImg.astype('uint8'), 1, np.pi / 180, 150, None, 0, 0)
		if lines is not None: # Assuming at least one line has been found  
			for oneLine in range(0,len(lines)): 
				# Go through the lines, one by one. 
				rho = lines[oneLine][0][0]
				theta = lines[oneLine][0][1]
				a = np.cos(theta)
				b = np.sin(theta)
				x0 = a * rho
				y0 = b * rho
				pt1 = (int(x0 + 1000*(-b)), int(y0 + 1000*(a)))
				pt2 = (int(x0 - 1000*(-b)), int(y0 - 1000*(a)))
				cv2.line(toDisplay, pt1, pt2, (0,0,255), 3, cv2.LINE_AA)


	return (toDisplay, image, grad_x, grad_y)