import numpy as np
import cv2

img = cv2.imread('comics.jpg')
imgrey = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
ret,thresh1 = cv2.threshold(imgrey,127,255,cv2.THRESH_BINARY_INV)

contours,heirarchy = cv2.findContours(thresh1,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)

for contour in contours:
  hull = cv2.convexHull(contour)
  cv2.drawContours(imgrey,[hull],-1,0,-1)

ret,thresh1 = cv2.threshold(imgrey,127,255,cv2.THRESH_BINARY_INV)
contours,heirarchy = cv2.findContours(thresh1,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)

for contour in contours:
  cv2.drawContours(img,[contour],-1,(0,255,0),3)

cv2.imwrite('threshold_image.png',img)