Add check that the images don't contain only zero values

Author: pulkkins

pysteps/motion/proesmans.py

@@ -57,7 +57,8 @@ def proesmans(input_images, lam=50.0, num_iter=100, num_levels=6, filter_std=0.0
     im = np.stack([im1, im2])
     im_min = np.min(im)
     im_max = np.max(im)
-    im = (im - im_min) / (im_max - im_min) * 255.0
+    if im_max - im_min > 1e-8:
+        im = (im - im_min) / (im_max - im_min) * 255.0
 
     if filter_std > 0.0:
         im[0, :, :] = gaussian_filter(im[0, :, :], filter_std)