import cv2

def light_removing(frame) :
  gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
  lab = cv2.cvtColor(frame, cv2.COLOR_BGR2LAB)
  L = lab[:,:,0]
  med_L = cv2.medianBlur(L, 99) # median filter
  invert_L = cv2.bitwise_not(med_L) # invert lightness
  composed = cv2.addWeighted(gray, 0.75, invert_L, 0.25, 0)
  return L, composed