title: keras "image_dim_ordering" configuration not working
body: <p>I have been trying to change the keras image dim order from tensorflow order to theano order. I modified <code>~/.keras/keras.json</code> file ,the line <code>"image_dim_ordering": "th"</code> is not working, but the line  <code>"backend": "theano"</code> configuration is working. </p>
  
  <pre><code>{
  "floatx": "float32",
  "epsilon": 1e-07,
  "backend": "theano",
  "image_dim_ordering": "th"  
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/R4jkI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/R4jkI.png" alt=""></a> </p>
  
  <p>And when I add <code>backend.image_dim_ordering('th')</code> in the beginning of the program,there is a new issue in weights loading. I'm sure the weight is using theano backend, and in "th" order.</p>
  
  <pre><code>ValueError: Layer weight shape (3,3,3,64) not compatible with provided weight shape(64,3,3,3)
  </code></pre>
  
  <p>original error without <code>backend.image_dim_ordering('th')</code> in the beginning of program:</p>
  
  <pre><code>Exception: Layer weight shape (3, 3, 640, 64) not compatible with provided weight shape (64, 3, 3, 3)
  </code></pre>
  
  <p>I am using python 2.7.12 ,the problem occurs both in win7 and Ubuntu 16.04 system.</p>