pyDistanceBetween2Lines-V2

# Find the minimum distance between two white lines
# Mike Kerry - Jan 2022 - [email protected]
# This is an improved algorithm that works in a wider set of cases

import cv2
import numpy as np

def getdist(a , b):
    # compute the square of the distance between two coordinates
    dsq = (a[0] - b[0]) ** 2 + (a[1] - b[1]) ** 2
    return dsq


img = cv2.imread("WhiteLines.jpg")

dims = img.shape
width = dims[1]
height = dims[0]
minsep = width // 20            # minimum separation allowed between lines is 5% of screen with
minsepsq = minsep * minsep
print("Width:", width, "  Height:", height)

cv2.imshow("img", img)

array_upper = []   # This array will hold all the coordinates of white pixels of the upper line
array_lower = []   # This array will hold all the coordinates of white pixels of the lower line

# Scan down the image, line by line, looking for white pixels
# separate into two arrays
for y, line in enumerate(img):      # y is line counter (vertical coordinate)
    for x, bgr in enumerate(line):  # x is the horizontal coordinate
        # Is this pixel white?
        if sum(bgr) > 384:  # look for pale pixels  (765 would be pure white, 0 is black)
            # Is this pixel close to the last pixel for upper line array? (if any)
            i = len(array_upper)
            if i and getdist((y, x), array_upper[i - 1]) > minsepsq:
                # this white pixel is not close to the previous pixel in array_upper
                # therefore it belongs in the array for the lower line
                array_lower.append((y, x))
            else:
                # pixel is near previous pixel in array_upper (or is the first white pixel found)
                # therefore it belongs to the array for the upper line
                array_upper.append((y, x))

# Find the closest distance between the two lines (i.e. the two arrays)
mindistsq = 999999          # square of the minimum distance so far
mincoord1 = (0, 0)
mincoord2 = (0, 0)

for coord1 in array_lower:
    for coord2 in array_upper:
        distsq = getdist(coord1, coord2)    # compute the distance squared, in pixels
        if distsq < mindistsq:
            mindistsq = distsq
            mincoord1 = coord1      # Remember the coordinates of the closest white points
            mincoord2 = coord2

# Make the closest points red
y, x = mincoord1
for my in range(5):
    for mx in range(5):
        img[y - 2 + my, x - 2 + mx] = (0, 0, 255)       # make pixels red

y, x = mincoord2
for my in range(5):
    for mx in range(5):
        img[y - 2 + my, x - 2 + mx] = (0, 0, 255)

# Draw a red line between the closest points
diffy = mincoord1[0] - mincoord2[0]     # vertical distance
diffx = mincoord1[1] - mincoord2[1]     # horizontal distance

for dy in range(diffy):
    y = mincoord2[0] + dy
    dx = int((diffx * dy) / diffy)
    x = mincoord2[1] + dx
    img[y][x] = (0, 0, 255)     # set pixel colour red

mindist = int(mindistsq ** 0.5)
print("Minimum distance beteween the lines is:", mindist)

cv2.imshow("img", img)
cv2.waitKey(0)