title: Reflection padding Conv2D
body: <p>I'm using keras to build a convolutional neural network for image segmentation and I want to use "reflection padding" instead of padding "same" but I cannot find a way to to do it in keras.</p>
  
  <pre><code>inputs = Input((num_channels, img_rows, img_cols))
  conv1=Conv2D(32,3,padding='same',kernel_initializer='he_uniform',data_format='channels_first')(inputs)
  </code></pre>
  
  <p>Is there a way to implement a reflection layer and insert it in a keras model ?</p>