title: ValueError: Argument must be a dense tensor - Python and TensorFlow
body: <p>I'm extracting some portions of my code that might be relevant to the issue I'm having:</p>
  
  <pre><code>from PIL import Image
  import tensorflow as tf
  
  data = Image.open('1-enhanced.png')
  ...
  ...
  raw_data = data
  raw_img = raw_data
  </code></pre>
  
  <p>I'm getting the following long message which I'm not sure how to analyze (do you have any idea on what's going on here):</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\op_def_library.py", line 490, in apply_op
      preferred_dtype=default_dtype)
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\ops.py", line 669, in convert_to_tensor
      ret = conversion_func(value, dtype=dtype, name=name, as_ref=as_ref)
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\constant_op.py", line 176, in _constant_tensor_conversion_function
      return constant(v, dtype=dtype, name=name)
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\constant_op.py", line 165, in constant
      tensor_util.make_tensor_proto(value, dtype=dtype, shape=shape, verify_shape=verify_shape))
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\tensor_util.py", line 376, in make_tensor_proto
      _GetDenseDimensions(values)))
  ValueError: Argument must be a dense tensor: &lt;PIL.PngImagePlugin.PngImageFile image mode=L size=150x150 at 0x1E07D3C0AC8&gt; - got shape [150, 150], but wanted [].
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "conv_visuals.py", line 54, in &lt;module&gt;
      x = tf.reshape(raw_data, shape=[-1,150,150,1])
    File "C:\Python35\lib\site-packages\tensorflow\python\ops\gen_array_ops.py", line 2448, in reshape
      name=name)
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\op_def_library.py", line 503, in apply_op
      as_ref=input_arg.is_ref).dtype.name
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\ops.py", line 669, in convert_to_tensor
      ret = conversion_func(value, dtype=dtype, name=name, as_ref=as_ref)
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\constant_op.py", line 176, in _constant_tensor_conversion_function
      return constant(v, dtype=dtype, name=name)
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\constant_op.py", line 165, in constant
      tensor_util.make_tensor_proto(value, dtype=dtype, shape=shape, verify_shape=verify_shape))
    File "C:\Python35\lib\site-packages\tensorflow\python\framework\tensor_util.py", line 376, in make_tensor_proto
      _GetDenseDimensions(values)))
  ValueError: Argument must be a dense tensor: &lt;PIL.PngImagePlugin.PngImageFile image mode=L size=150x150 at 0x1E07D3C0AC8&gt; - got shape [150, 150], but wanted [].
  </code></pre>
  
  <p>Thanks.</p>