python - Change Number of Channel to a fixed value for 4d shape images

Question

My current input shape is [4, 3, 32, 32] and I want to reduce the second parameter to 1 which will eventually become [4, 1, 32, 32]. Are there any methods that can achieve this using numpy? Thank you so much for your help in advance.

question from:https://stackoverflow.com/questions/65856889/change-number-of-channel-to-a-fixed-value-for-4d-shape-images

Answer 1

It depends on the function you want to use for reduction. Usually the ufunc add or sum is used to reduce axis. Keepdims=True will ensure keeping the 4 axis intact after reduction. -

x = np.random.random((4, 3, 32, 32))

np.add.reduce(x,1,keepdims=True)
#(4,1,32,32)

x.sum(1, keepdims=True)
#(4,1,32,32)