QR.hs

{-# LANGUAGE OverloadedStrings #-}

import Data.QRCode
import Data.Text (Text, pack, unpack)
import qualified Data.Text as T
import qualified Data.Text.IO as T
import Data.Word8
import System.Environment
import System.IO

main = do args <- getArgs
          qr (head args) >>= mapM_ T.putStrLn

qr :: String -> IO [Text]
qr s = do qcode <- encodeString s Nothing QR_ECLEVEL_L QR_MODE_EIGHT True
          let words = toMatrix qcode
              dimh = length . head $ words
              border = replicate dimh 0x00 :: [Word8]
              words' = border : words ++ [border]
              bordered = map (\arr -> 0x00 : arr ++ [0x00]) words'
          return $ map qrFmt bordered

qrFmt :: [Word8] -> Text
qrFmt q = T.append (foldr (\c t -> colorise c `T.append` t) "" q) "\x1b[49m"
  where colorise c = T.append "\x1b[" $ if c == 0x01
                       then "40m  " -- black
                       else "47m  " -- white

I don't remember why this uses Text. Unicode I guess!