Tensorflow: visualize convolutional filters (conv1) in Cifar10 model

gist_cifar10_train.py

from math import sqrt

def put_kernels_on_grid (kernel, pad = 1):

  '''Visualize conv. filters as an image (mostly for the 1st layer).
  Arranges filters into a grid, with some paddings between adjacent filters.

  Args:
    kernel:            tensor of shape [Y, X, NumChannels, NumKernels]
    pad:               number of black pixels around each filter (between them)

  Return:
    Tensor of shape [1, (Y+2*pad)*grid_Y, (X+2*pad)*grid_X, NumChannels].
  '''
  # get shape of the grid. NumKernels == grid_Y * grid_X
  def factorization(n):
    for i in range(int(sqrt(float(n))), 0, -1):
      if n % i == 0:
        if i == 1: print('Who would enter a prime number of filters')
        return (i, int(n / i))
  (grid_Y, grid_X) = factorization (kernel.get_shape()[3].value)
  print ('grid: %d = (%d, %d)' % (kernel.get_shape()[3].value, grid_Y, grid_X))

  x_min = tf.reduce_min(kernel)
  x_max = tf.reduce_max(kernel)
  kernel = (kernel - x_min) / (x_max - x_min)

  # pad X and Y
  x = tf.pad(kernel, tf.constant( [[pad,pad],[pad, pad],[0,0],[0,0]] ), mode = 'CONSTANT')

  # X and Y dimensions, w.r.t. padding
  Y = kernel.get_shape()[0] + 2 * pad
  X = kernel.get_shape()[1] + 2 * pad

  channels = kernel.get_shape()[2]

  # put NumKernels to the 1st dimension
  x = tf.transpose(x, (3, 0, 1, 2))
  # organize grid on Y axis
  x = tf.reshape(x, tf.stack([grid_X, Y * grid_Y, X, channels]))

  # switch X and Y axes
  x = tf.transpose(x, (0, 2, 1, 3))
  # organize grid on X axis
  x = tf.reshape(x, tf.stack([1, X * grid_X, Y * grid_Y, channels]))

  # back to normal order (not combining with the next step for clarity)
  x = tf.transpose(x, (2, 1, 3, 0))

  # to tf.image_summary order [batch_size, height, width, channels],
  #   where in this case batch_size == 1
  x = tf.transpose(x, (3, 0, 1, 2))

  # scaling to [0, 255] is not necessary for tensorboard
  return x


#
# ... and somewhere inside "def train():" after calling "inference()"
#

# Visualize conv1 kernels
with tf.variable_scope('conv1'):
  tf.get_variable_scope().reuse_variables()
  weights = tf.get_variable('weights')
  grid = put_kernels_on_grid (weights)
  tf.image.summary('conv1/kernels', grid, max_outputs=1)

@Mithun-Aggarwal, @2016gary. Sorry, I didn't check the comments in a while.
It does not make much sense to visualize conv layer 2+, except maybe for checking for dead filters.
Besides, humans can visualize 3 channels as RGB, but will not be able to interpret 64 channels.

Now, if you're really into it, here's what you can do. Let's say you have 32 input channels on the 2nd layer out 64 output channels. Instead of having one grid with 64 color squares, make 64 grids with 32 grayscale channels. Each grid == a filter. Again, it would be be hard to interpret, but easy to spot dead filters.
I may implement that some time in the future.

The code by @kitovyj should use tf.stack, instead of tf.pack.

@headdab, I already implemented changes suggested by @kitovyj into this gist, and changed pack to stack according to API of the recent TF versions.

 raise ValueError("Variable %s does not exist, or was not created with "
                 "tf.get_variable(). Did you mean to set "
                  "reuse=tf.AUTO_REUSE in VarScope?" % name)

Create the tensor to initialize the variable with default value.

ValueError: Variable conv1/weights does not exist, or was not created with tf.get_variable(). Did you mean to set reuse=tf.AUTO_REUSE in VarScope?

I got this error. What should I do?