Take the dirty code of «getText» and turn it into a relatively clean module exposing pages, that can be retrieved all at once or by page number (numbered human-style, starting from 1)
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3 changed files with 201 additions and 132 deletions
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@ -21,9 +21,10 @@ library
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, PDF.EOL
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, PDF.Object
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, PDF.Output
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, PDF.Pages
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, PDF.Parser
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, PDF.Text
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, PDF.Update
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, PDF.Parser
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other-modules: Data.ByteString.Char8.Util
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, PDF.Body
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-- other-extensions:
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@ -34,6 +35,7 @@ library
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, mtl
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, text
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, utf8-string
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, zlib
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hs-source-dirs: src
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ghc-options: -Wall
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default-language: Haskell2010
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@ -1,141 +1,37 @@
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{-# LANGUAGE NamedFieldPuns #-}
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{-# LANGUAGE OverloadedStrings #-}
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import Codec.Compression.Zlib (decompress)
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import Control.Monad (foldM)
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import Control.Monad.RWS (RWST(..), ask, evalRWST, get, modify)
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import Control.Monad.Writer (tell)
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import Data.ByteString (ByteString)
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import qualified Data.ByteString.Char8 as BS (pack, putStrLn, readFile)
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import qualified Data.ByteString.Lazy as Lazy (fromStrict, toStrict)
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import Data.Map (Map, (!))
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import qualified Data.Map as Map (empty, insert, lookup, toList)
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import qualified Data.ByteString.Char8 as BS (putStrLn, readFile)
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import qualified Data.Map as Map (toList)
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import PDF (Document(..), parseDocument)
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import PDF.CMap (CMap, CMappers, cMap, emptyCMap)
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import PDF.Object (
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Content(..), Dictionary, DirectObject(..), IndirectObjCoordinates(..)
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, Object(..), Name(..), Structure(..)
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,)
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import PDF.Output (ObjectId(..))
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import PDF.Text (PageContents(..), pageContents)
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import PDF.Object (Content)
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import PDF.Pages (Page(..), get, getAll)
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import PDF.Update (unify)
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import System.Environment (getArgs)
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import System.IO (hPutStrLn, stderr)
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import Text.Printf (printf)
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import System.Exit (die)
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import System.IO (BufferMode(..), hSetBuffering, stdout)
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type CachedCMaps = Map ObjectId CMap
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type T a = RWST Content [ByteString] CachedCMaps [] a
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onDoc :: FilePath -> (Content -> Either String a) -> IO a
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onDoc inputFile f = do
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content <- fmap (unify . updates) . parseDocument <$> BS.readFile inputFile
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case content >>= f of
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Left someError -> die someError
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Right value -> return value
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list :: [a] -> T a
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list l = RWST (\_ s -> fillContext s <$> l)
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where
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fillContext s a = (a, s, [])
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displayPage :: Page -> IO ()
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displayPage = mapM_ BS.putStrLn . contents
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handleError :: ObjectId -> a -> String -> T a
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handleError objectId defaultValue s =
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(tell . replicate 1 $ BS.pack message) >> return defaultValue
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where
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message = printf "Object #%d : %s" (getObjectId objectId) s
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extractText :: Object -> T ()
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extractText object = do
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pageDict <- dict object
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cMappers <- loadCMappers =<< getFont pageDict
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contentsId <- target =<< key "Contents" pageDict
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contents <- stream =<< getObject contentsId
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either (handleError contentsId ()) (tell . chunks) (pageContents cMappers contents)
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stream :: Object -> T ByteString
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stream (Stream {header, streamContent}) = return $
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case Map.lookup (Name "Filter") header of
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Just (NameObject (Name "FlateDecode")) ->
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Lazy.toStrict . decompress . Lazy.fromStrict $ streamContent
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_ -> streamContent
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stream _ = list []
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getFont :: Dictionary -> T Dictionary
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getFont pageDict =
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key "Resources" pageDict
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>>= dict . Direct
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>>= key "Font"
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>>= follow
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>>= dict
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cache :: (ObjectId -> T CMap) -> ObjectId -> T CMap
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cache loader objectId = do
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loaded <- get
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case Map.lookup objectId loaded of
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Just value -> return value
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Nothing -> do
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value <- loader objectId
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modify (Map.insert objectId value) >> return value
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loadFont :: ObjectId -> T CMap
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loadFont objectId =
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getObject objectId
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>>= dict
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>>= key "ToUnicode"
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>>= follow
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>>= stream
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>>= either (handleError objectId emptyCMap) return . cMap
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loadCMappers :: Dictionary -> T CMappers
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loadCMappers = foldM loadCMapper Map.empty . Map.toList
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where
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loadCMapper :: CMappers -> (Name, DirectObject) -> T CMappers
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loadCMapper output (name, Reference (IndirectObjCoordinates {objectId})) = do
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flip (Map.insert name) output <$> cache loadFont objectId
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loadCMapper output _ = return output
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getObject :: ObjectId -> T Object
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getObject objectId = do
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content <- ask
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return (objects content ! objectId)
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key :: String -> Dictionary -> T DirectObject
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key keyName dictionary =
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case Map.lookup (Name keyName) dictionary of
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Just obj -> return obj
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_ -> list []
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target :: DirectObject -> T ObjectId
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target (Reference (IndirectObjCoordinates {objectId})) = return objectId
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target _ = list []
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follow :: DirectObject -> T Object
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follow directObject = target directObject >>= getObject
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dict :: Object -> T Dictionary
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dict (Direct (Dictionary dictionary)) = return dictionary
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dict _ = list []
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pagesList :: T ObjectId
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pagesList = do
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root <- dict =<< follow =<< key "Root" . trailer . docStructure =<< ask
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pages <- dict =<< follow =<< key "Pages" root
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case Map.lookup (Name "Kids") pages of
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Just (Array kids) -> list $ filterObjectIds kids
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_ -> list []
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filterObjectIds :: [DirectObject] -> [ObjectId]
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filterObjectIds objects = do
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object <- objects
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case object of
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Reference (IndirectObjCoordinates {objectId}) -> [objectId]
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_ -> []
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listTextObjects :: Document -> [ByteString]
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listTextObjects (Document {updates}) =
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snd =<< evalRWST rwsMain (unify updates) Map.empty
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where
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rwsMain =
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pagesList >>= getObject >>= extractText
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wholeDoc :: FilePath -> IO ()
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wholeDoc inputFile = do
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pages <- onDoc inputFile getAll
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mapM_ (displayPage . snd) $ Map.toList pages
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singlePage :: FilePath -> Int -> IO ()
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singlePage inputFile pageNumber =
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onDoc inputFile (`get` pageNumber) >>= displayPage
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main :: IO ()
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main = do
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[inputFile] <- getArgs
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result <- parseDocument <$> BS.readFile inputFile
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case result of
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Left parseError -> hPutStrLn stderr $ show parseError
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Right doc -> mapM_ BS.putStrLn $ listTextObjects doc
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hSetBuffering stdout LineBuffering
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args <- getArgs
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case args of
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[inputFile] -> wholeDoc inputFile
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[inputFile, pageNumber] -> singlePage inputFile (read pageNumber)
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_ -> die "Syntax: getText INPUT_FILE [PAGE_NUMBER]"
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171
src/PDF/Pages.hs
Executable file
171
src/PDF/Pages.hs
Executable file
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@ -0,0 +1,171 @@
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{-# LANGUAGE NamedFieldPuns #-}
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module PDF.Pages (
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Page(..)
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, get
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, getAll
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) where
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import Codec.Compression.Zlib (decompress)
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import Control.Monad (foldM)
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import Control.Monad.RWS (RWST(..), ask, evalRWST, mapRWST, modify)
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import qualified Control.Monad.RWS as RWS (get)
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import Data.ByteString (ByteString)
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import qualified Data.ByteString.Lazy as Lazy (fromStrict, toStrict)
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import Data.Map (Map, (!))
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import qualified Data.Map as Map (empty, fromList, insert, lookup, toList)
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import PDF.CMap (CMap, CMappers, cMap)
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import PDF.Object (
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Content(..), Dictionary, DirectObject(..), IndirectObjCoordinates(..)
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, Object(..), Name(..), Structure(..)
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,)
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import PDF.Output (ObjectId(..))
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import PDF.Text (pageContents)
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import Prelude hiding (fail)
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import Text.Printf (printf)
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type CachedCMaps = Map ObjectId CMap
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type T = RWST Content () CachedCMaps (Either String)
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data Page = Page {
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contents :: [ByteString]
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, source :: ObjectId
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}
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infixl 1 \\=
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(\\=) :: T a -> (a -> Either String b) -> T b
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x \\= f = mapRWST ((\(a, s, w) -> (\b -> (b, s, w)) <$> f a) =<<) x
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infixl 1 //=
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(//=) :: Either String a -> (a -> T b) -> T b
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(//=) (Left e) _ = RWST (\_ _ -> Left e)
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(//=) (Right a) f = f a
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lift :: Either String a -> T a
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lift x = x //= return
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expected :: Show a => String -> a -> Either String b
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expected name = Left . printf "Not a %s: %s" name . show
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stream :: Object -> Either String ByteString
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stream (Stream {header, streamContent}) = Right $
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case Map.lookup (Name "Filter") header of
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Just (NameObject (Name "FlateDecode")) ->
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Lazy.toStrict . decompress . Lazy.fromStrict $ streamContent
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_ -> streamContent
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stream obj = expected "stream" obj
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getResource :: DirectObject -> T Dictionary
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getResource (Dictionary dictionary) = return dictionary
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getResource (Reference (IndirectObjCoordinates {objectId})) =
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getObject objectId \\= dict
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getResource directObject =
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lift $ expected "resource (dictionary or reference)" directObject
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getFont :: Dictionary -> T Dictionary
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getFont pageDict =
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key "Resources" pageDict
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//= getResource
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\\= key "Font"
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>>= follow
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\\= dict
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cache :: (ObjectId -> T CMap) -> ObjectId -> T CMap
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cache loader objectId =
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(maybe load return . Map.lookup objectId) =<< RWS.get
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where
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load = do
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value <- loader objectId
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modify $ Map.insert objectId value
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return value
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loadFont :: ObjectId -> T CMap
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loadFont objectId =
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(getObject objectId
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\\= dict
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\\= key "ToUnicode"
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>>= follow)
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\\= stream
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\\= cMap
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loadCMappers :: Dictionary -> T CMappers
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loadCMappers = foldM loadCMapper Map.empty . Map.toList
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where
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loadCMapper :: CMappers -> (Name, DirectObject) -> T CMappers
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loadCMapper output (name, Reference (IndirectObjCoordinates {objectId})) =
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flip (Map.insert name) output <$> cache loadFont objectId
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--maybe output (flip (Map.insert name) output) <$> cache loadFont objectId
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loadCMapper output _ = return output
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getObject :: ObjectId -> T Object
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getObject objectId = do
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content <- ask
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return (objects content ! objectId)
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key :: String -> Dictionary -> Either String DirectObject
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key keyName dictionary =
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maybe (Left errorMessage) Right (Map.lookup (Name keyName) dictionary)
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where
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errorMessage =
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printf "Key %s not found in dictionary %s" keyName (show dictionary)
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target :: DirectObject -> Either String ObjectId
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target (Reference (IndirectObjCoordinates {objectId})) = Right objectId
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target directObject = expected "reference" directObject
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many :: DirectObject -> [DirectObject]
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many (Array l) = l
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many directObject = [directObject]
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follow :: DirectObject -> T Object
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follow directObject = target directObject //= getObject
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dict :: Object -> Either String Dictionary
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dict (Direct (Dictionary dictionary)) = Right dictionary
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dict obj = expected "dictionary" obj
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dictObject :: String -> Dictionary -> T Dictionary
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dictObject keyName dictionary = key keyName dictionary //= follow \\= dict
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pagesList :: T [ObjectId]
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pagesList = do
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root <- dictObject "Root" . trailer . docStructure =<< ask
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pages <- dictObject "Pages" root
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case Map.lookup (Name "Kids") pages of
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Just (Array kids) -> return $ getReferences kids
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_ -> return []
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getReferences :: [DirectObject] -> [ObjectId]
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getReferences objects = do
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object <- objects
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case object of
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Reference (IndirectObjCoordinates {objectId}) -> [objectId]
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_ -> []
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extractText :: Object -> T [ByteString]
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extractText object = do
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pageDict <- lift $ dict object
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cMappers <- loadCMappers =<< getFont pageDict
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let objects = ((many <$> (key "Contents" pageDict)) :: Either String [DirectObject])
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concat <$> (objects //= (mapM $ loadContent cMappers))
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where
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loadContent :: CMappers -> DirectObject -> T [ByteString]
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loadContent cMappers directObject =
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follow directObject \\= stream \\= pageContents cMappers
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loadPage :: ObjectId -> T Page
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loadPage source =
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(\contents -> Page {contents, source}) <$> (extractText =<< getObject source)
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getAll :: Content -> Either String (Map Int Page)
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getAll content = fst <$> evalRWST getPages content Map.empty
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where
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numbered = Map.fromList . zip [1..]
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getPages = numbered <$> (mapM loadPage =<< pagesList)
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get :: Content -> Int -> Either String Page
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get content pageNumber
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| pageNumber < 1 = Left "Pages start at 1"
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| otherwise = fst <$> evalRWST getPage content Map.empty
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where
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firstPage [] = lift $ Left "Page is out of bounds"
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firstPage (p:_) = loadPage p
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getPage = drop (pageNumber - 1) <$> pagesList >>= firstPage
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