This menu provides several options for importing and exporting your tilemaps (map layers) from/to .tilemap files and images. .tilemap files don't include any information about tilesets, layer names, overhead tiles, or anything else. If you want to export non-tilemap data or a whole map from one game to another that can be done by copying data lump files; ask about it.

Be careful when overwriting existing layers! This can't be undone, so backup your game first if unsure.

Exporting to a tile-a-pixel .png/.bmp file allows doing very basic map editing of a single map layer with a graphics editor, such as adding the shape of continents or islands on a world map before importing it in again. Pixels with indistinguishable colors may correspond to different tiles in the tileset.

Export as full image draws the map at full resolution, optionally with NPCs, as a .png file.
