More efficient tiling

[emiliolr]

Given the sheer size of many of the 2018 mosaics, we might want to look for a more efficient library than PIL for reading in mosaics. For instance, much of each mosaic is empty space (to fill a rectangle), which doesn’t really need to be loaded/tiled!

• Here's a (poorly documented) library for reading in and tiling large images: large-image. Seems to be substantially more memory-efficient.
  • See the page on extracting tiles or iterating through an image to get tiles. Seems like this could be super helpful!
• The tiling approach in DeepForest help here.
  • In particular, see their function used for tiling.

If doing this will require too much of a code overhaul, IT WILL NOT BE WORTH IT!

[emiliolr]

Tiling is efficient enough that I don't think we'll have to go down this route.