code: import numpy
  import argparse
  import cv2
  
  image = cv2.imread('pikachu.jpg')
  cv2.imshow("Original", image)
  gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
  cv2.imshow("Gray", gray)
  
  eq = cv2.equalizeHist(gray)
  ##cv2.imshow("Gray EQ", eq)
  
  #display two images in a figure
  cv2.imshow("Histogram Equalization", numpy.hstack([gray, eq]))
  
  cv2.imwrite("pikachu_eq.jpg", numpy.hstack([gray, eq]))
  
  
  if(cv2.waitKey(0)==27):
      cv2.destroyAllWindows()
  
apis: numpy.hstack