code: import numpy as np
  import cv2
  
  img = cv2.imread('exercise_images/lion.jpg')
  
  img_yuv = cv2.cvtColor(img, cv2.COLOR_BGR2YUV)
  
  # equalize the histogram of the Y channel
  img_yuv[:,:,1] = cv2.equalizeHist(img_yuv[:,:,0])
  
  # convert the YUV image back to RGB format
  img_output = cv2.cvtColor(img_yuv, cv2.COLOR_YUV2BGR)
  res = np.hstack((img,img_output))
  
  cv2.imwrite('newlionc.jpg',res)
  
  cv2.imshow('Color input image', img)
  cv2.imshow('Histogram equalized', img_output)
  
  cv2.waitKey(0)
  
apis: numpy.hstack