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{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE OverloadedRecordDot #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
module Main where
import Control.Arrow (second)
import Control.Exception (Exception, throw, throwIO)
import Control.Monad (join, when)
import Data.Attoparsec.Text qualified as A
import Data.ByteString.Lazy qualified as LB
import Data.List
import Data.Map qualified as M
import Data.Maybe (fromMaybe)
import Data.String (IsString (fromString))
import Data.Text qualified as T
import Data.Text.Encoding qualified as T
import Debug.Trace
import System.Directory
import System.FilePath
import System.IO.Temp (withSystemTempDirectory)
import System.Process.Typed
import Text.Printf (printf)
import Text.Read (readMaybe)
main :: IO ()
main = do
let input = "0000001.pdf"
ocr input
debug :: Show a => String -> a -> a
debug s x =
trace (printf "%s: %s\n" s (show x)) x
ocr :: FilePath -> IO ()
ocr input = do
withSystemTempDirectory input $ \tmp -> do
let fn suffix = tmp </> takeBaseName input <> suffix
pdfInfo <- parsePdfInfo <$> sh (printf "pdfinfo '%s'" input)
pdfImages <- parsePdfImages <$> sh (printf "pdfimages -list '%s'" input)
hasText <-
(not . T.null) . T.strip . T.decodeUtf8 . LB.toStrict
<$> sh (printf "pdftotext '%s' -" input)
when (not hasText) do
let isScan =
length pdfImages == pdfInfo.numPages
&& all ((pdfInfo.pageSize ==) . imageSize) pdfImages
if isScan
then sh_ (printf "pdfimages '%s' '%s' -tiff" input (fn ""))
else sh_ (printf "pdftoppm '%s' '%s' -r 300 -tiff" input (fn "-%d.pdf"))
imageFiles <- sort <$> listDirectory tmp
-- XXX add DPI information to image so that resulting pdf preserves DPI
mapM_
( \(pdfImage, imageFile) ->
sh_
( printf
"convert -density %dx%d -units PixelsPerInch '%s' '%s'"
pdfImage.xPpi
pdfImage.yPpi
(tmp </> imageFile)
(tmp </> imageFile)
)
)
(zip pdfImages imageFiles)
pdfFiles <- mapM (ocr1 tmp . (tmp </>)) imageFiles
sh_ ("pdfunite " ++ intercalate " " (map (printf "'%s'" . (tmp </>)) pdfFiles ++ [printf "'%s'" (tmp </> input)]))
copyFile input (input <.> "bak")
copyFile (tmp </> input) ("." <> input)
renameFile ("." <> input) input
ocr1 :: FilePath -> FilePath -> IO FilePath
ocr1 tmp input = do
sh_
( printf
"tesseract '%s' '%s' pdf"
(tmp </> input)
(tmp </> takeBaseName input)
)
pure (takeBaseName input <.> "pdf")
data PdfInfo = PdfInfo
{ numPages :: Int,
pageSize :: (Double, Double)
}
deriving (Show)
data PdfInfoException = PdfInfoException
deriving (Show)
instance Exception PdfInfoException
parsePdfInfo :: LB.ByteString -> PdfInfo
parsePdfInfo out' =
fromMaybe (throw PdfInfoException) $ do
numPages <- readMaybe . T.unpack =<< M.lookup "Pages" kvs
pageSize <-
rightToMaybe . A.parseOnly pageSizeParser
=<< M.lookup "Page size" kvs
pure PdfInfo {..}
where
out = T.decodeUtf8 (LB.toStrict out')
kvs =
M.fromList
. map (second T.stripStart)
. map (second T.tail . T.break (== ':'))
. filter (not . T.null)
. T.lines
$ out
pageSizeParser =
(,)
<$> (A.double <* A.string " x ")
<*> (A.double <* A.string " pts (A4)")
<* A.endOfInput
type PdfImages = [PdfImage]
data PdfImage = PdfImage
{ page :: Int,
num :: Int,
type_ :: String,
width :: Int,
height :: Int,
color :: String,
comp :: Int,
bpc :: Int,
enc :: String,
interp :: String,
object :: Int,
id :: Int,
xPpi :: Int,
yPpi :: Int,
size :: String,
ratio :: String
}
deriving (Show)
imageSize :: PdfImage -> (Double, Double)
imageSize (PdfImage {..}) =
let f ppi p = 72 * fromIntegral p / fromIntegral ppi
in (f xPpi width, f yPpi height)
data PdfImagesException = PdfImagesException
deriving (Show)
instance Exception PdfImagesException
data ProcessException = ProcessException Int LB.ByteString
deriving (Show)
instance Exception ProcessException
parsePdfImages :: LB.ByteString -> PdfImages
parsePdfImages out' =
map
( \(page' : num' : type_ : width' : height' : color : comp' : bpc' : enc : interp : object' : id' : xPpi' : yPpi' : size : ratio : []) ->
PdfImage
{ page = read page',
num = read num',
width = read width',
height = read height',
comp = read comp',
bpc = read bpc',
object = read object',
id = read id',
xPpi = read xPpi',
yPpi = read yPpi',
..
}
)
. map (map T.unpack)
. map T.words
. drop 2
. filter (not . T.null)
. T.lines
$ out
where
out = T.decodeUtf8 (LB.toStrict out')
sh :: String -> IO LB.ByteString
sh cmd = do
-- printf "+ %s\n" cmd
(exitCode, out, err) <- readProcess (fromString cmd)
case exitCode of
ExitSuccess -> return out
ExitFailure exitCode' -> throwIO $ ProcessException exitCode' err
sh_ :: String -> IO ()
sh_ = fmap (\_ -> ()) . sh
rightToMaybe :: Either e a -> Maybe a
rightToMaybe = either (const Nothing) Just
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