Wiener filter divide by zero errors if uniform patch in image

[OisinMoran]

The wiener filter from scipy.signal is encountering divide by zero errors/warnings for images that have a patch of uniform colour. Any help in fixing this or working around it would be greatly appreciated!

Reproducing code example:

import numpy as np
import scipy.signal

image = np.random.randint(0, 256, size=(8, 8, 3))
image[2:6, 2:6, :] = 137 # can be any number
wiener_filtered = scipy.signal.wiener(image.astype('float32'), mysize=(3, 3, 1))

Error message:

/home/paperspace/anaconda3/lib/python3.6/site-packages/scipy/signal/signaltools.py:950: RuntimeWarning: divide by zero encountered in true_divide
  res *= (1 - noise / lVar)
/home/paperspace/anaconda3/lib/python3.6/site-packages/scipy/signal/signaltools.py:950: RuntimeWarning: invalid value encountered in multiply
  res *= (1 - noise / lVar)

Scipy/Numpy/Python version information:

0.19.1 1.13.1 sys.version_info(major=3, minor=6, micro=2, releaselevel='final', serial=0)

Image of error and example problem image: