This was originally going to be part of Transparent Objects but it works differently, requires PyTK, may hurt CPU usage, and for the sake of publicity, I made it a new mod.
Note: things like buildings, tunnels, non-choppable trees, etc. are part of the map, so you can't just draw them partially transparent. As a result, transparency with this mod is not as smooth as one might like (see screenshots).
What this mod does is, when a farmer is completely behind map tiles, it sets the tiles above and around the player to three separate levels of transparency:
The two tiles covering the player (InnerTransparency)
The tiles surrounding the player except for the corners (OuterTransparency)
The four corners surrounding the player (CornerTransparency)
The three transparencies are independent and configurable in the config.json file (created when you first run with this mod). Transparency values should be a decimal between 0 and 1 (0 being invisible and 1 being opaque).
The player house and greenhouse are not a part of the map and do not work with this mod.
I'm not sure it works in multiplayer, I'm sure someone will let me know :)
I'm not sure what sort of hit the CPU takes, it seems to run fine on my beast.
Requires SMAPI and PyTK, does not use Harmony.
Compatible with Mod Updater for automatic updates.
Code is at https://github.com/aedenthorn/StardewValleyMods.
If you want to complain or ask for help or help me test my mods, you can visit my Discord server.
A list of all my mods for Stardew Valley is available at https://www.nexusmods.com/stardewvalley/articles/895.