text: import cv2 as cv
  import keras.backend as K
  import numpy as np
  
  from utils import custom_loss
  
  if __name__ == '__main__':
      file_id = '07647'
      filename = 'images/samples/{}.jpg'.format(file_id)
      bgr_img = cv.imread(filename)
      y_true = cv.cvtColor(bgr_img, cv.COLOR_BGR2GRAY)
      cv.imwrite( 'images/samples/{}_gray.jpg'.format(file_id), y_true)
      y_true = y_true / 255.
      y_true = y_true.astype(np.float32)
  
      filename = 'images/samples/{}_out.jpg'.format(file_id)
      y_pred = cv.imread(filename, 0)
      y_pred = y_pred / 255.
      y_pred = y_pred.astype(np.float32)
      loss = custom_loss(y_true, y_pred)
      print(K.eval(loss))
  