draw lines and distances on image opencv python

There's nothing I can do because I don't have your original image. But you can read my code and maybe get an idea. For distance, I don't know what you mean, so I gave an example on how to get the distance from the top left corner to the bottom left corner. You can apply other points or apply it as a ratio according to your requirements.

import cv2
import numpy as np

img = cv2.imread('untitled.png')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
ret, threshold = cv2.threshold(gray,150,255,cv2.THRESH_BINARY)
im, contours, hierarchy = cv2.findContours(threshold,cv2.RETR_TREE,cv2.CHAIN_APPROX_NONE)
area = sorted(contours, key=cv2.contourArea, reverse=True)
c = area[0]
rect = cv2.minAreaRect(c)
box = cv2.boxPoints(rect)
print(box)
box = np.int0(box)
cv2.drawContours(img,[box],0,(0,0,255),2)
extreme_left = tuple(c[c[:, :, 0].argmin()][0])
extreme_top = tuple(c[c[:, :, 1].argmin()][0])
x1 = box[1,0]
y1 = box[1,1]
x2 = box[0,0]
y2 = box[0,1]
distance = np.sqrt( (x1 - x2)**2 + (y1 - y2)**2 )
font = cv2.FONT_HERSHEY_SIMPLEX
cv2.putText(img,'Distance: '+str(distance),(1,300), font, 0.5,(255,255,255),2,cv2.LINE_AA)
cv2.circle(img, (x2,y2), 5, (255, 0, 0), -1)
cv2.circle(img, (x1,y1), 5, (255, 0, 0), -1)
cv2.imshow('image', img)