text: import cv2
  import numpy as np
  
  def onTrackbarChange(x):
      pass
  
  img = np.zeros((300, 512, 3), np.uint8)
  
  cv2.namedWindow('image')
  
  cv2.createTrackbar('B', 'image', 0, 255, onTrackbarChange)
  cv2.createTrackbar('G', 'image', 0, 255, onTrackbarChange)
  cv2.createTrackbar('R', 'image', 0, 255, onTrackbarChange)
  
  while(True):
      cv2.imshow('image', img)
      k = cv2.waitKey(1) & 0xFF
      if k == 27:
          break
      b = cv2.getTrackbarPos('B', 'image')
      g = cv2.getTrackbarPos('G', 'image')
      r = cv2.getTrackbarPos('R', 'image')
      
      img[:] = (b, g, r)
  
  cv2.destroyAllWindows()
  