drawing lines and distance to them on image opencv python - python-3.x

Question

I encountered such a problem: I can not draw lines on the image where the color was determined, and also find out the distance to this place. Help to make it as in the image below:
My code:
import cv2
import numpy as np
from PIL import ImageGrab
while True:
screen = np.array(ImageGrab.grab(bbox=(0,40,800,640)))
rgb_screen = cv2.cvtColor(screen, cv2.COLOR_BGR2RGB)
lower = np.array([72, 160, 160])
upper = np.array([112, 249, 249])
mask = cv2.inRange(rgb_screen, lower, upper)
output = cv2.bitwise_and(rgb_screen, rgb_screen, mask=mask)
cv2.imshow('window', output)
if cv2.waitKey(25) & 0xFF == ord('q'):
cv2.destroyAllWindows()
break

Answer 1

I can't help much because I do not have your original image. But you could read my code and maybe get an idea. For distance I do not know what u mean, so I made an example on how to get distance of top left corner to bottom left. You can apply other points or apply it as ratio depanding on your demands.
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)