text: Title: Gallery examples use Matplotlib in a hybrid way (explicit vs. implicit interfaces).
  Body: ### Description:
  
  I would suggest using the "object-oriented (OO) style" (as opposed to pyplot-style) across the gallery.
  
  This issue replicates https://github.com/datacarpentry/image-processing/issues/319, which I opened for the skimage-based lesson by Data Carpentry.