def load_npz(filename):
"""
Load an .npz Image, this .npz file must have at least two arrays
* data: the data array
* dimnames: the dimension names of the corresponding grid
* affine: the affine transformation of grid
The remaining arrays of .npz file are stored as the 'extra' attribute of the Image.
"""
npzobj = np.load(filename)
im = Image(npzobj['data'], CoordinateMap.from_affine(Affine(npzobj['affine']),
list(npzobj['dimnames']),
npzobj['data'].shape))
im.extra = {}
for f in npzobj.files:
if f not in ['affine', 'dimnames', 'data']:
im.extra[f] = npzobj[f]
return im
