  Neutron imaging is an invaluable noninvasive technique for exploring new
science and assisting industrial manufacture. However, state-of-the-art neutron
facilities are extremely expensive and inconvenient to access, while the flux
of portable neutron sources is not strong enough to form even a static image
within an acceptable time frame. It is hard to obtain images with both high
spatial resolution and energy resolution together. Here, based on classical
amplitude modulation, we demonstrate single-pixel imaging with neutrons with
specially designed masks and, further, obtain energy-selective images with a
spallation neutron source. Images of real complex objects with 100 {\mu}m
spatial resolution and 10 {\mu}s time resolution (corresponding to 0.4% at 1
{\AA}) have been obtained using a 3He single-pixel detector. Even when the
neutron counts in the detector plane were lowered to 1000 per modulation
pattern on average, a clear image was still obtained. The experimental setup is
simple, inexpensive and easy to operate, thus our scheme points to a new path
for neutron imaging, especially for portable radioactive neutron sources of low
intensity, which should be of great benefit for diagnostic analysis in biology,
materials science, and industrial processes.
