title: Is the input of `tf.image.resize_images` must have static shape?
body: <p>I run the code below, it raises an <code>ValueError: 'images' contains no shape</code>. Therefore I have to add the line behind <code>#</code> to set the static shape, but <code>img_raw</code> may have different shapes and this line makes the <code>tf.image.resize_images</code> out of effect.
  I just want to turn images with different shapes to [227,227,3]. How should I do that?</p>
  
  <pre><code>def tf_read(file_queue):
      reader = tf.WholeFileReader()
      file_name, content = reader.read(file_queue)
      img_raw = tf.image.decode_image(content,3)
      # img_raw.set_shape([227,227,3])
      img_resized = tf.image.resize_images(img_raw,[227,227])
      img_shape = tf.shape(img_resized)
      return file_name, img_resized,img_shape
  </code></pre>