title: How to re-use ImageDataGenerator fit params (e.g. featurewise_center, featurewise_std_normalization) in evaluation?
body: <p>I use ImageDataGenerator .fit() to normalize training data. But then there is no elegant way to perform .standardize() on real when I deploy the model (different running code then training).</p>
  
  <p>I realize I can extract the normalization params, save them somewhere and then perform the normalization myself but then it would be easier to write it myself to begin with.</p>
  
  <p>Is there a way to this in the current design?
  Is there a way to do .standardize() long after the training code has completed?</p>