aboutsummaryrefslogtreecommitdiff
path: root/src/Text/Pandoc/ImageSize.hs
blob: 963057b6fb6cea577f929646b1a9e1922e0a4f61 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
{-# LANGUAGE OverloadedStrings, ScopedTypeVariables  #-}
{-# OPTIONS_GHC -fno-warn-type-defaults #-}
{-
  Copyright (C) 2011-2014 John MacFarlane <jgm@berkeley.edu>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
    more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc., 59
    Temple Place, Suite 330, Boston, MA  02111-1307  USA
-}

{- |
Module      : Text.Pandoc.ImageSize
Copyright   : Copyright (C) 2011-2014 John MacFarlane
License     : GNU GPL, version 2 or above

Maintainer  : John MacFarlane <jgm@berkeley.edu>
Stability   : alpha
Portability : portable

Functions for determining the size of a PNG, JPEG, or GIF image.
-}
module Text.Pandoc.ImageSize ( ImageType(..), imageType, imageSize,
                    sizeInPixels, sizeInPoints ) where
import Data.ByteString (ByteString, unpack)
import qualified Data.ByteString.Char8 as B
import qualified Data.ByteString.Lazy as BL
import Control.Applicative
import Control.Monad
import Data.Bits
import Data.Binary
import Data.Binary.Get
import Text.Pandoc.Shared (safeRead)
import qualified Data.Map as M
import Text.Pandoc.Compat.Except
import Text.Pandoc.Error
import Control.Monad.Trans
import Data.Maybe (fromMaybe)

-- quick and dirty functions to get image sizes
-- algorithms borrowed from wwwis.pl

data ImageType = Png | Gif | Jpeg | Pdf | Eps deriving Show

data ImageSize = ImageSize{
                     pxX   :: Integer
                   , pxY   :: Integer
                   , dpiX  :: Integer
                   , dpiY  :: Integer
                   } deriving (Read, Show, Eq)


imageType :: ByteString -> Maybe ImageType
imageType img = case B.take 4 img of
                     "\x89\x50\x4e\x47" -> return Png
                     "\x47\x49\x46\x38" -> return Gif
                     "\xff\xd8\xff\xe0" -> return Jpeg  -- JFIF
                     "\xff\xd8\xff\xe1" -> return Jpeg  -- Exif
                     "%PDF"             -> return Pdf
                     "%!PS"
                       | (B.take 4 $ B.drop 1 $ B.dropWhile (/=' ') img) == "EPSF"
                                        -> return Eps
                     _                  -> (hush . Left) "Unknown image type"

imageSize :: ByteString -> Maybe ImageSize
imageSize img = do
  t <- imageType img
  case t of
       Png  -> pngSize img
       Gif  -> gifSize img
       Jpeg -> jpegSize img
       Eps  -> epsSize img
       Pdf  -> Nothing  -- TODO

defaultSize :: (Integer, Integer)
defaultSize = (72, 72)

sizeInPixels :: ImageSize -> (Integer, Integer)
sizeInPixels s = (pxX s, pxY s)

sizeInPoints :: ImageSize -> (Integer, Integer)
sizeInPoints s = (pxX s * 72 `div` dpiX s, pxY s * 72 `div` dpiY s)

epsSize :: ByteString -> Maybe ImageSize
epsSize img = do
  let ls = takeWhile ("%" `B.isPrefixOf`) $ B.lines img
  let ls' = dropWhile (not . ("%%BoundingBox:" `B.isPrefixOf`)) ls
  case ls' of
       []    -> mzero
       (x:_) -> case B.words x of
                     (_:_:_:ux:uy:[]) -> do
                        ux' <- safeRead $ B.unpack ux
                        uy' <- safeRead $ B.unpack uy
                        return ImageSize{
                            pxX  = ux'
                          , pxY  = uy'
                          , dpiX = 72
                          , dpiY = 72 }
                     _ -> mzero

pngSize :: ByteString -> Maybe ImageSize
pngSize img = do
  let (h, rest) = B.splitAt 8 img
  guard $ h == "\x8a\x4d\x4e\x47\x0d\x0a\x1a\x0a" ||
          h == "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a"
  let (i, rest') = B.splitAt 4 $ B.drop 4 rest
  guard $ i == "MHDR" || i == "IHDR"
  let (sizes, rest'') = B.splitAt 8 rest'
  (x,y) <- case map fromIntegral $ unpack $ sizes of
                ([w1,w2,w3,w4,h1,h2,h3,h4] :: [Integer]) -> return
                    ((shift w1 24) + (shift w2 16) + (shift w3 8) + w4,
                     (shift h1 24) + (shift h2 16) + (shift h3 8) + h4)
                _ -> (hush . Left) "PNG parse error"
  let (dpix, dpiy) = findpHYs rest''
  return $ ImageSize { pxX  = x, pxY = y, dpiX = dpix, dpiY = dpiy }

findpHYs :: ByteString -> (Integer, Integer)
findpHYs x =
  if B.null x || "IDAT" `B.isPrefixOf` x
     then (72,72) -- default, no pHYs
     else if "pHYs" `B.isPrefixOf` x
          then let [x1,x2,x3,x4,y1,y2,y3,y4,u] = map fromIntegral
                                               $ unpack $ B.take 9 $ B.drop 4 x
                   factor = if u == 1 -- dots per meter
                               then \z -> z * 254 `div` 10000
                               else const 72
               in  ( factor $ (shift x1 24) + (shift x2 16) + (shift x3 8) + x4,
                     factor $ (shift y1 24) + (shift y2 16) + (shift y3 8) + y4 )
          else findpHYs $ B.drop 1 x  -- read another byte

gifSize :: ByteString -> Maybe ImageSize
gifSize img = do
  let (h, rest) = B.splitAt 6 img
  guard $ h == "GIF87a" || h == "GIF89a"
  case map fromIntegral $ unpack $ B.take 4 rest of
       [w2,w1,h2,h1] -> return ImageSize {
                          pxX  = shift w1 8 + w2,
                          pxY  = shift h1 8 + h2,
                          dpiX = 72,
                          dpiY = 72
                          }
       _             -> (hush . Left) "GIF parse error"

jpegSize :: ByteString -> Maybe ImageSize
jpegSize img = do
  let (hdr, rest) = B.splitAt 4 img
  guard $ B.length rest >= 14
  case hdr of
       "\xff\xd8\xff\xe0" -> jfifSize rest
       "\xff\xd8\xff\xe1" -> exifSize $ B.takeWhile (/= '\xff') rest
       _                  -> mzero

jfifSize :: ByteString -> Maybe ImageSize
jfifSize rest = do
  let [dpiDensity,dpix1,dpix2,dpiy1,dpiy2] = map fromIntegral
                                           $ unpack $ B.take 5 $ B.drop 9 $ rest
  let factor = case dpiDensity of
                    1 -> id
                    2 -> \x -> (x * 254 `div` 10)
                    _ -> const 72
  let dpix = factor (shift dpix1 8 + dpix2)
  let dpiy = factor (shift dpiy1 8 + dpiy2)
  (w,h) <- findJfifSize rest
  return $ ImageSize { pxX = w, pxY = h, dpiX = dpix, dpiY = dpiy }

findJfifSize :: ByteString -> Maybe (Integer,Integer)
findJfifSize bs = do
  let bs' = B.dropWhile (=='\xff') $ B.dropWhile (/='\xff') bs
  case B.uncons bs' of
       Just (c,bs'') | c >= '\xc0' && c <= '\xc3' -> do
         case map fromIntegral $ unpack $ B.take 4 $ B.drop 3 bs'' of
              [h1,h2,w1,w2] -> return (shift w1 8 + w2, shift h1 8 + h2)
              _             -> (hush . Left) "JPEG parse error"
       Just (_,bs'') ->  do
         case map fromIntegral $ unpack $ B.take 2 bs'' of
              [c1,c2] -> do
                let len = shift c1 8 + c2
                -- skip variables
                findJfifSize $ B.drop len bs''
              _       -> (hush . Left) "JPEG parse error"
       Nothing -> (hush . Left) "Did not find length record"

exifSize :: ByteString -> Maybe ImageSize
exifSize bs = hush . runGet header $ bl
  where bl = BL.fromChunks [bs]
        header = runExceptT $ exifHeader bl
-- NOTE:  It would be nicer to do
-- runGet ((Just <$> exifHeader) <|> return Nothing)
-- which would prevent pandoc from raising an error when an exif header can't
-- be parsed.  But we only get an Alternative instance for Get in binary 0.6,
-- and binary 0.5 ships with ghc 7.6.

exifHeader :: BL.ByteString -> ExceptT String Get ImageSize
exifHeader hdr = do
  _app1DataSize <- lift getWord16be
  exifHdr <- lift getWord32be
  unless (exifHdr == 0x45786966) $ throwError "Did not find exif header"
  zeros <- lift getWord16be
  unless (zeros == 0) $ throwError "Expected zeros after exif header"
  -- beginning of tiff header -- we read whole thing to use
  -- in getting data from offsets:
  let tiffHeader = BL.drop 8 hdr
  byteAlign <- lift getWord16be
  let bigEndian = byteAlign == 0x4d4d
  let (getWord16, getWord32, getWord64) =
        if bigEndian
           then (getWord16be, getWord32be, getWord64be)
           else (getWord16le, getWord32le, getWord64le)
  let getRational = do
        num <- getWord32
        den <- getWord32
        return $ fromIntegral num / fromIntegral den
  tagmark <- lift getWord16
  unless (tagmark == 0x002a) $ throwError "Failed alignment sanity check"
  ifdOffset <- lift getWord32
  lift $ skip (fromIntegral ifdOffset - 8) -- skip to IDF
  numentries <- lift  getWord16
  let ifdEntry :: ExceptT String Get (TagType, DataFormat)
      ifdEntry = do
       tag <- fromMaybe UnknownTagType . flip M.lookup tagTypeTable
                <$> lift getWord16
       dataFormat <- lift getWord16
       numComponents <- lift getWord32
       (fmt, bytesPerComponent) <-
             case dataFormat of
                  1  -> return (UnsignedByte . runGet getWord8, 1)
                  2  -> return (AsciiString, 1)
                  3  -> return (UnsignedShort . runGet getWord16, 2)
                  4  -> return (UnsignedLong . runGet getWord32, 4)
                  5  -> return (UnsignedRational . runGet getRational, 8)
                  6  -> return (SignedByte . runGet getWord8, 1)
                  7  -> return (Undefined . runGet getWord8, 1)
                  8  -> return (SignedShort . runGet getWord16, 2)
                  9  -> return (SignedLong . runGet getWord32, 4)
                  10 -> return (SignedRational . runGet getRational, 8)
                  11 -> return (SingleFloat . runGet getWord32 {- TODO -}, 4)
                  12 -> return (DoubleFloat . runGet getWord64 {- TODO -}, 8)
                  _  -> throwError $ "Unknown data format " ++ show dataFormat
       let totalBytes = fromIntegral $ numComponents * bytesPerComponent
       payload <- lift $
                    if totalBytes <= 4 -- data is right here
                     then fmt <$>
                          (getLazyByteString (fromIntegral totalBytes) <*
                          skip (4 - totalBytes))
                     else do  -- get data from offset
                          offs <- getWord32
                          return $ fmt $ BL.take (fromIntegral totalBytes) $
                                   BL.drop (fromIntegral offs) tiffHeader
       return (tag, payload)
  entries <- sequence $ replicate (fromIntegral numentries) ifdEntry
  subentries <- case lookup ExifOffset entries of
                      Just (UnsignedLong offset) -> do
                        pos <- lift bytesRead
                        lift $ skip (fromIntegral offset - (fromIntegral pos - 8))
                        numsubentries <- lift getWord16
                        sequence $
                           replicate (fromIntegral numsubentries) ifdEntry
                      _ -> return []
  let allentries = entries ++ subentries
  (width, height) <- case (lookup ExifImageWidth allentries,
                           lookup ExifImageHeight allentries) of
                          (Just (UnsignedLong w), Just (UnsignedLong h)) ->
                            return (fromIntegral w, fromIntegral h)
                          _ -> return defaultSize
                               -- we return a default width and height when
                               -- the exif header doesn't contain these
  let resfactor = case lookup ResolutionUnit allentries of
                        Just (UnsignedShort 1) -> (100 / 254)
                        _ -> 1
  let xres = maybe 72 (\(UnsignedRational x) -> floor $ x * resfactor)
             $ lookup XResolution allentries
  let yres = maybe 72 (\(UnsignedRational x) -> floor $ x * resfactor)
             $ lookup YResolution allentries
  return $ ImageSize{
                    pxX  = width
                  , pxY  = height
                  , dpiX = xres
                  , dpiY = yres }

data DataFormat = UnsignedByte Word8
                | AsciiString BL.ByteString
                | UnsignedShort Word16
                | UnsignedLong Word32
                | UnsignedRational Rational
                | SignedByte Word8
                | Undefined Word8
                | SignedShort Word16
                | SignedLong Word32
                | SignedRational Rational
                | SingleFloat Word32
                | DoubleFloat Word64
                deriving (Show)

data TagType = ImageDescription
             | Make
             | Model
             | Orientation
             | XResolution
             | YResolution
             | ResolutionUnit
             | Software
             | DateTime
             | WhitePoint
             | PrimaryChromaticities
             | YCbCrCoefficients
             | YCbCrPositioning
             | ReferenceBlackWhite
             | Copyright
             | ExifOffset
             | ExposureTime
             | FNumber
             | ExposureProgram
             | ISOSpeedRatings
             | ExifVersion
             | DateTimeOriginal
             | DateTimeDigitized
             | ComponentConfiguration
             | CompressedBitsPerPixel
             | ShutterSpeedValue
             | ApertureValue
             | BrightnessValue
             | ExposureBiasValue
             | MaxApertureValue
             | SubjectDistance
             | MeteringMode
             | LightSource
             | Flash
             | FocalLength
             | MakerNote
             | UserComment
             | FlashPixVersion
             | ColorSpace
             | ExifImageWidth
             | ExifImageHeight
             | RelatedSoundFile
             | ExifInteroperabilityOffset
             | FocalPlaneXResolution
             | FocalPlaneYResolution
             | FocalPlaneResolutionUnit
             | SensingMethod
             | FileSource
             | SceneType
             | UnknownTagType
             deriving (Show, Eq, Ord)

tagTypeTable :: M.Map Word16 TagType
tagTypeTable = M.fromList
  [ (0x010e, ImageDescription)
  , (0x010f, Make)
  , (0x0110, Model)
  , (0x0112, Orientation)
  , (0x011a, XResolution)
  , (0x011b, YResolution)
  , (0x0128, ResolutionUnit)
  , (0x0131, Software)
  , (0x0132, DateTime)
  , (0x013e, WhitePoint)
  , (0x013f, PrimaryChromaticities)
  , (0x0211, YCbCrCoefficients)
  , (0x0213, YCbCrPositioning)
  , (0x0214, ReferenceBlackWhite)
  , (0x8298, Copyright)
  , (0x8769, ExifOffset)
  , (0x829a, ExposureTime)
  , (0x829d, FNumber)
  , (0x8822, ExposureProgram)
  , (0x8827, ISOSpeedRatings)
  , (0x9000, ExifVersion)
  , (0x9003, DateTimeOriginal)
  , (0x9004, DateTimeDigitized)
  , (0x9101, ComponentConfiguration)
  , (0x9102, CompressedBitsPerPixel)
  , (0x9201, ShutterSpeedValue)
  , (0x9202, ApertureValue)
  , (0x9203, BrightnessValue)
  , (0x9204, ExposureBiasValue)
  , (0x9205, MaxApertureValue)
  , (0x9206, SubjectDistance)
  , (0x9207, MeteringMode)
  , (0x9208, LightSource)
  , (0x9209, Flash)
  , (0x920a, FocalLength)
  , (0x927c, MakerNote)
  , (0x9286, UserComment)
  , (0xa000, FlashPixVersion)
  , (0xa001, ColorSpace)
  , (0xa002, ExifImageWidth)
  , (0xa003, ExifImageHeight)
  , (0xa004, RelatedSoundFile)
  , (0xa005, ExifInteroperabilityOffset)
  , (0xa20e, FocalPlaneXResolution)
  , (0xa20f, FocalPlaneYResolution)
  , (0xa210, FocalPlaneResolutionUnit)
  , (0xa217, SensingMethod)
  , (0xa300, FileSource)
  , (0xa301, SceneType)
  ]