def shiftZ(af):
"""
af: 3D array in fourier space
return Z shifted array
"""
nz = af.shape[0]
cz = nz // 2
bf = N.empty_like(af)
bf[cz:] = af[:(nz - cz)]
bf[:(nz - cz)] = af[cz:]
return bf
def arr_invert(arr):
canvas = N.empty_like(arr)
canvas[:] = U.max(arr)
return canvas - arr