numpy util

# change channel

import numpy as np
a=np.array([[1,2,3],[4,5,6]])
print(a)
print(a.shape)

b=a[:,[2,1,0]]
print(b)

注意不是np.transpose，这个是交换axises

new axis，然后复制

np.transpose(np.tile(img, (3,1,1)), (1,2,0))