Custom median pooling in tensorflow

Question

I am trying to implement a median pooling layer in tensorflow.

However there is neither tf.nn.median_pool and neither tf.reduce_median.

Is there a way to implement such pooling layer with the python api ?

Answer 1

You could use something like:

patches = tf.extract_image_patches(tensor, [1, k, k, 1], ...)
m_idx = int(k*k/2+1)
top = tf.top_k(patches, m_idx, sorted=True)
median = tf.slice(top, [0, 0, 0, m_idx-1], [-1, -1, -1, 1])

To accommodate even sized median kernels and multiple channels, you will need to extend this, but this should get you most of the way.