Codec.ImageType

Infers an image's type by looking at its initial values and comparing against some magic bytes:

>>> :set -XOverloadedStrings
>>> import Codec.ImageType
>>> import System.IO
>>> import qualified Data.ByteString as B
>>> 
>>> h <- openFile "/tmp/1_webp_ll.webp" ReadMode
>>> bytes <- hGet h 32
>>> B.isInfixOf "RIFF" bytes
True
>>> bytes
"RIFF\144h\SOH\NULWEBPVP8L\131h\SOH\NUL/\143\SOHK\DLE\141\&8l\219F\146\224"
>>> getFileType "/tmp/1_webp_ll.webp"
Just "webp"

Some other examples:

>>> import System.Process
>>> import System.Directory
>>> import Control.Monad
>>> let findTiffs = lines <$> readProcess "locate" ["*.tiff"] ""
>>> length <$> findTiffs
25
>>> findTiffs >>= filterM doesFileExist >>= mapM getFileType
[Just "tiff",Just "tiff", …
>>> sequence_ <$> (findTiffs >>= filterM doesFileExist >>= mapM getFileType)
Just ()

Actions

getFileType :: FilePath -> IO (Maybe String)

Gets a ginel possible file types based on fairly arbitrary tie breaking.

>>> import System.Directory
>>> import Control.Monad
>>> getDirectoryContents "." >>= filterM doesFileExist >>= mapM getFileType
[Just "rast",Just "jpeg",Nothing,Just "webp",Just "gif",Just "pgm",Just "webp",Nothing,Just "webp",Just "exr"]

getFileTypes :: FilePath -> IO [String]

Gets possible file types. Returns empty list if nothing is found, otherwise a list of matches.

>>> import System.Directory
>>> import Control.Monad
>>> getDirectoryContents "." >>= filterM doesFileExist >>= mapM getFileTypes
[["rast"],["jpeg"],[],["webp"],["gif"],["pgm"],["webp"],[],["webp"],["exr"]]

Predicates

isJpeg :: FilePath -> IO Bool

Checks if file is jpeg.

>>> import Codec.ImageType
>>> import Control.Monad
>>> import System.Directory
>>> 
>>> 
>>> getDirectoryContents "." >>= filterM doesFileExist >>= filterM isJpeg
["file2.jpeg","file1.jpeg"]

isPng :: FilePath -> IO Bool

Checks if file is png.

isGif :: FilePath -> IO Bool

Checks if file is gif.

isTiff :: FilePath -> IO Bool

Checks if file is tiff.

isRgb :: FilePath -> IO Bool

Checks if file is rgb.

isPbm :: FilePath -> IO Bool

Checks if file is pbm.

isPgm :: FilePath -> IO Bool

Checks if file is pgm.

isPpm :: FilePath -> IO Bool

Checks if file is ppm.

isRast :: FilePath -> IO Bool

Checks if file is rast.

isXbm :: FilePath -> IO Bool

Checks if file is xbm.

isBmp :: FilePath -> IO Bool

Checks if file is bmp.

isWebp :: FilePath -> IO Bool

Checks if file is webp.

isExr :: FilePath -> IO Bool

Checks if file is exr.

Getting file type name

testJpeg :: ByteString -> Maybe String

Joint Photographic Experts Group (JPEG). Returns Just jpeg if file satisfies check.

testPng :: ByteString -> Maybe String

Portable Network Graphics (PNG). Returns Just png if file satisfies check against magic number 89 50 4e 47 0d 0a 1a 0a.

testGif :: ByteString -> Maybe String

Graphics Interchange Format (GIF). Returns Just gif if file satisfies check against magic number GIF87a and GIF89a.

testTiff :: ByteString -> Maybe String

Tagged Image File Format (TIFF). Returns Just tiff if first short is II or MM.

testRgb :: ByteString -> Maybe String

SGI image library. Checks magic number (decimal value 474 as a short) that identifies file as an SGI image file and then returns Just rgb.

testPbm :: ByteString -> Maybe String

PBM (portable bitmap). Returns Just pbm if file satisfies check.

testPgm :: ByteString -> Maybe String

PGM (portable graymap). Returns Just pgm if file satisfies check.

testPpm :: ByteString -> Maybe String

PPM (portable pixmap). Returns Just ppm if file satisfies check.

testRast :: ByteString -> Maybe String

Sun raster file. Returns Just rast if file satisfies check.

testXbm :: ByteString -> Maybe String

X bitmap (X10 or X11). Returns Just xbm if file satisfies check.

testBmp :: ByteString -> Maybe String

Bitmap (BMP) file format. Returns Just bmp if file satisfies check.

testWebp :: ByteString -> Maybe String

WebP. Returns Just webp if file satisfies check.

testExr :: ByteString -> Maybe String

OpenEXR. Returns Just exr if file satisfies check.