It appears that the problem was that numpy fft returns a complex array, which gave an error when trying to display it. By extracting only the real parts of the array, it seems to work fine. This is a sample of what I was trying to do:import numpy
from numpy import fft
from skimage import io, data
import matplotlib.pyplot as plot
im = data.coffee()
f = fft.fft2(im)
f2 = fft.ifft2(f)
r = numpy.real(f2)
plot.imshow(r)
plot.show()