I saw this screenshot and I was wondering if is there a tool to take a screenshot of an entire building?
Terraria Map Generator is an automatic option where you just crop your building from; another option is to take screenshots manually and stitching them together. You can use F11 to hide the UI, although you need to kill monsters and replace your character if you only want to see the building.
Terrafirma is a map viewer, too, but can use* textures to display the world, thus being closer to a screeshot than 1-pixel-per-tile map viewers.
*edit: you have to check “use textures” in the menu first, and be zoomed in enough to see the textures.
It looks like the game is just set to a very high resolution.
You can press F11 to remove the HUD.