How To Construct 2d Array From 2d Arrays

I need to reconstruct 2d array(from image colour channel) of the specific shape from a number of smaller arrays: import numpy as np from PIL import Image def blockshaped(arr, nrow

Solution 1:

Reshape to split the first axis into three axes of lengths 2,2,8, keeping the second axis as it is. Then, permute axes with rollaxis/swapaxes/transpose and a final reshape to have 16 x 16 shape -

n_a2.reshape(2,2,8,8).swapaxes(1,2).reshape(16,16)

Sample run for verification -

In [46]: c = np.random.randint(11,99,(16,16))

In [47]: n_a = blockshaped(c,8,8) # dividing array into 4 subarrays
    ...: n_a2 = np.concatenate(n_a, axis = 0) #concatenate arrays
    ...: 

In [48]: out = n_a2.reshape(2,2,8,8).swapaxes(1,2).reshape(16,16)

In [49]: np.allclose(out, c)
Out[49]: True