CODEWITHSUNDEEP
pythontensorflow
Fabian
Fabian

Reputation: 3448

Enlarge a tensor in tensorflow

I'm searching for a tensorflow python method to enlarge (resize) a tensor to double every element in each feature map along both axis e.g.:

 ([[1, 2, 3],
   [4, 5, 6],
   [7, 8, 9]])

=>

 ([[1, 1, 2, 2, 3, 3],
   [1, 1, 2, 2, 3, 3],
   [4, 4, 5, 5, 6, 6],
   [4, 4, 5, 5, 6, 6],
   [7, 7, 8, 8, 9, 9],
   [7, 7, 8, 8, 9, 9]])

I saw tf.tile and tf.pad but I can not figure out how to use this methods to get that result.

Thanks for any hint!

UPDATE:

Thanks to sygi for that helpful hint here is the shape independent solution that works in jupyter notebook using python3 kernel:

import tensorflow as tf
import numpy as np

i = np.array([[1, 2, 3],
              [4, 5, 6],
              [7, 8, 9]])

j = np.array([[1,  2,  3,  4],
              [5,  6,  7,  8],
              [9, 10, 11, 12]])

k = np.array([[1, 2],
              [3, 4],
              [5, 6]])

a = tf.placeholder(tf.int64, shape=(None, None))
a_shape = tf.shape(a)

b = tf.reshape(a, [a_shape[0], a_shape[1], 1])
c = tf.tile(b, [1, 1, 2])
d = tf.reshape(c, [a_shape[0], a_shape[1]*2])

e = tf.reshape(d, [a_shape[0], a_shape[1]*2, 1])
f = tf.tile(e, [1, 1, 2])
g = tf.transpose(f, [0, 2, 1])

h = tf.reshape(g, [a_shape[0]*2, a_shape[1]*2])

session = tf.InteractiveSession()
session.run(tf.initialize_all_variables())

print(h.eval(feed_dict={a: i}))
print(h.eval(feed_dict={a: j}))
print(h.eval(feed_dict={a: k}))

session.close()

results in

[[1 1 2 2 3 3]
 [1 1 2 2 3 3]
 [4 4 5 5 6 6]
 [4 4 5 5 6 6]
 [7 7 8 8 9 9]
 [7 7 8 8 9 9]]

[[ 1  1  2  2  3  3  4  4]
 [ 1  1  2  2  3  3  4  4]
 [ 5  5  6  6  7  7  8  8]
 [ 5  5  6  6  7  7  8  8]
 [ 9  9 10 10 11 11 12 12]
 [ 9  9 10 10 11 11 12 12]]

[[1 1 2 2]
 [1 1 2 2]
 [3 3 4 4]
 [3 3 4 4]
 [5 5 6 6]
 [5 5 6 6]]

Upvotes: 2

Views: 4970

Answers (2)

rank1
rank1

Reputation: 1038

Just use tf.image.ResizeMethod with Nearest Neighbor interpolation

array = tf.image.resize_images(old_array, (old_size*2, old_size*2),
                               method=tf.image.ResizeMethod.NEAREST_NEIGHBOR)

Input to the method must be 4-D Tensor of shape [batch, height, width, channels] or 3-D Tensor of shape [height, width, channels].

https://www.tensorflow.org/api_docs/python/tf/image/resize

Upvotes: 0

sygi
sygi

Reputation: 4647

a = tf.convert_to_tensor([[1, 2, 3],
                          [4, 5, 6],
                          [7, 8, 9]])
b = tf.reshape(a, [3, 3, 1])
c = tf.tile(b, [1, 1, 2])
d = tf.reshape(c, [3, 6])
print(d.eval())
array([[1, 1, 2, 2, 3, 3],
       [4, 4, 5, 5, 6, 6],
       [7, 7, 8, 8, 9, 9]], dtype=int32)

e = tf.reshape(d, [3, 6, 2])
f = tf.tile(e, [1, 1, 2])
g = tf.transpose(f, [0, 2, 1])
print(g.eval())
array([[[1, 1, 2, 2, 3, 3],
        [1, 1, 2, 2, 3, 3]],

       [[4, 4, 5, 5, 6, 6],
        [4, 4, 5, 5, 6, 6]],

       [[7, 7, 8, 8, 9, 9],
        [7, 7, 8, 8, 9, 9]]], dtype=int32)

h = tf.reshape(g, [6, 6])
print(h.eval())
array([[1, 1, 2, 2, 3, 3],
       [1, 1, 2, 2, 3, 3],
       [4, 4, 5, 5, 6, 6],
       [4, 4, 5, 5, 6, 6],
       [7, 7, 8, 8, 9, 9],
       [7, 7, 8, 8, 9, 9]], dtype=int32)

You can get a shape of the a tensor (if it's defined) using:

shape = a.get_shape().as_list()

Upvotes: 2

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