convert a batch of images from RGB to greyscale

batch_rgb2gray.py

import tensorflow as tf
import numpy as np

def rgb2gray(rgb):
      return np.dot(rgb[...,:3], [0.2989, 0.5870, 0.1140])

def batch_rgb2gray(rgb):
  color = rgb
  rgb_t = tf.transpose(rgb, [0, 2, 3, 1]) 
  sess = tf.Session()
  np_color = rgb_t
  with sess.as_default():
    rgb_np = rgb_t.eval()
  grey = rgb2gray(rgb_np)
  
  return grey