surf:save

surf:save([file, format])

• file (string)
  File path
• format (string)
  Image format (see below)

Saves the surface into the image format and returns the image data (string).
If a file path is not supplied, it doesn't save to a file.
Supported formats:

• "nft" (npaintpro and sketch)
• "nfp" (default)(ComputerCraft paint)
• "rif" (Riko4 image format)
• "bmp" (24-bit non-bitmasked only)