Need help with a opencv program written in python

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I got a code on the internet which works with raspberry pi 3 and Pi camera. I want to modify a portion of it. I want to display on the camera the distance the colored object the code identifies is from the middle of the streaming video.

The code I have streams a video that recognizes red color and puts a red dot on the object. The code is below;

# import the necessary packages

from picamera.array import PiRGBArray

from picamera import PiCamera

import time

import cv2

import numpy as np

# initialize the camera and grab a reference to the raw camera capture

camera = PiCamera()

camera.resolution = (480, 320)

camera.framerate = 30

camera.hflip = True

rawCapture = PiRGBArray(camera, size=(480, 320))

# allow the camera to warmup

time.sleep(0.1)

# capture frames from the camera

for frame in camera.capture_continuous(rawCapture, format="bgr", use_video_port=True):

    # grab the raw NumPy array representing the image, then initialize the timestamp

    # and occupied/unoccupied text

        image = frame.array

        blur = cv2.blur(image, (3,3))

        #hsv to complicate things, or stick with BGR
        #hsv = cv2.cvtColor(blur,cv2.COLOR_BGR2HSV)
        #thresh = cv2.inRange(hsv,np.array((0, 200, 200)), np.array((20, 255, 255)))

        lower = np.array([4,10,120],dtype="uint8")
        #upper = np.array([225,88,50], dtype="uint8")
        upper = np.array([90,100,255], dtype="uint8")

        thresh = cv2.inRange(blur, lower, upper)
        thresh2 = thresh.copy()

        # find contours in the threshold image
        image, contours,hierarchy = cv2.findContours(thresh,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

        # finding contour with maximum area and store it as best_cnt
        max_area = 0
        best_cnt = 1
        for cnt in contours:
                area = cv2.contourArea(cnt)
                if area > max_area:
                        max_area = area
                        best_cnt = cnt

        # finding centroids of best_cnt and draw a circle there
        M = cv2.moments(best_cnt)
        cx,cy = int(M['m10']/M['m00']), int(M['m01']/M['m00'])
        #if best_cnt>1:
        cv2.circle(blur,(cx,cy),10,(100,100,255),-1)
        # show the frame
        cv2.imshow("Frame", blur)
        #cv2.imshow('thresh',thresh2)
        key = cv2.waitKey(1) & 0xFF

    # clear the stream in preparation for the next frame
        rawCapture.truncate(0)

    # if the `q` key was pressed, break from the loop
        if key == ord("q"):
            break