title: Load multiple images to 4D tensor
body: <p>I would like to load multiple images from a directory and then stack them in <strong>4D</strong> <strong>tensor</strong>. I wrote the following code:</p>
  
  <pre><code>import tensorflow as tf
  import matplotlib.image as mpimg
  import matplotlib.pyplot as plt
  import os
  img=tf.Variable(tf.zeros([134,65,147,1]),dtype=tf.float32)
  sess=tf.Session()
  model=tf.global_variables_initializer()
  dir_path = os.path.dirname('C:\\Users\\E6410\\Documents\\Masterarbeit\\specconvneu\\')
  for i in range(134):
      filename = dir_path + "\\Spec_Test("+str(i+1)+").png"
      image = mpimg.imread(filename)
      image = tf.Variable(image,dtype=tf.float32)
      sess.run(model)
      image=tf.reshape(image,[65,147,1])
      img[i+1,:,:,:].assign(image)
      sess.run(img)
      sess.run(image)
  </code></pre>
  
  <p>The number of images is 134. Every image has a height of 65 and a width of 147. They have one channel.
  I run my code and had the following Error:</p>
  
  <pre><code>FailedPreconditionError: Attempting to use uninitialized value Variable_344
       [[Node: Variable_344/read = Identity[T=DT_FLOAT, _class=["loc:@Variable_344"], _device="/job:localhost/replica:0/task:0/cpu:0"](Variable_344)]]
  </code></pre>
  
  <p>I understand that the compiler is trying to read the variable before initializing the variable. I tried to initialize it with different ways but always the same error. Could you help to correct the error?</p>