imshow fills an entire "unit" in the grid. I'd like to overlay two
imshow's on top of each other, but in a non-destructive manner. One
way of doing this would be to modify the behavior of imshow so that it
only fills a portion of each "unit" in the grid. For example, in the
first imshow, I'd fill everything below the diagonal and in the second
imshow, I'd fill everything above the diagonal.
Would this type of modification to AxesImage be feasible? Or should I
just (manually) make a PolyCollection for each imshow? I'd still want
interpolations to work as expected, but where filling (or not) is
restricted to a region within the "unit". Generally, I think this
could be a nice addition to mpl, but if there is a more typical way of
visualizing two imshows on the same axis, I might try that instead.