Should encoding="PNG" be default?

[banesullivan]

I noticed that JPEG seems to be the default encoding when opening a tile source. With the addition of the Jupyter visualizer in #1065, it may benefit users to have encoding="PNG" be the default to avoid opaque/black tiles outside of the image bounds:

Default	encoding='PNG'

[banesullivan]

I could also have the tile endpoint force PNG encoding in #1065, but I'm trying to let all configurations be entirely controlled by the source instance itself as maybe a user wants JPEG or some other encoding

[manthey]

Maybe on tiles sources with projections a PNG default, but changing this on non-projection sources increases data volume and would be a seriously breaking change. Sadly, although the jpeg standard supports having an alpha channel, essentially no one supports it.

[banesullivan]

Maybe on tiles sources with projections a PNG default

+1, this makes the most sense. I'll work to implement this in a dedicated PR