hsexif-0.6.0.5: EXIF handling library in pure Haskell

Safe HaskellNone
LanguageHaskell2010

Graphics.HsExif

Contents

Description

Ability to work with the EXIF data contained in JPEG files.

Synopsis

Documentation

EXIF parsing from JPEG files. EXIF tags are enumerated as ExifTag values, check exposureTime for instance. If you use the predefined ExifTag values, you don't care about details of the ExifTag type, however you should check out the ExifValue type.

Regarding the ExifTag type there is however a field of that type that may interest you: prettyPrinter. It's a function that'll format nicely an exif value for that exif tag as a String. For instance for the flash ExifTag, it'll say whether the flash was fired or not, if there was return light and so on.

Generally speaking, you start from a JPEG file, you can parse its exif tags as a Map of ExifTag to ExifValue using parseExif or parseFileExif. You can enumerate the map or lookup the tags that interest you.

There are also a couple of higher-level helpers like getOrientation, getDateTimeOriginal, wasFlashFired and getGpsLatitudeLongitude.

When building on Windows if you have trouble with the iconv library, you may build without that dependency: cabal install -f-iconv. That way you loose nice decoding of the EXIF User Comment though.

Main functions

parseFileExif :: FilePath -> IO (Either String (Map ExifTag ExifValue)) Source

Read EXIF data from the file you give. It's a key-value map.

parseExif :: ByteString -> Either String (Map ExifTag ExifValue) Source

Read EXIF data from a lazy bytestring.

Higher-level helper functions

readExifDateTime :: String -> Maybe LocalTime Source

Decode an EXIF date time value. Will return Nothing in case parsing fails.

getDateTimeOriginal :: Map ExifTag ExifValue -> Maybe LocalTime Source

Extract the date and time when the picture was taken from the EXIF information.

getOrientation :: Map ExifTag ExifValue -> Maybe ImageOrientation Source

Extract the image orientation from the EXIF information. Will return Nothing on parse error.

data ImageOrientation Source

Constructors

Normal 
Mirror 
Rotation RotationDirection 
MirrorRotation RotationDirection 

Instances

data RotationDirection Source

Constructors

MinusNinety 
Ninety 
HundredAndEighty 

Instances

getGpsLatitudeLongitude :: Map ExifTag ExifValue -> Maybe (Double, Double) Source

Extract the GPS latitude and longitude where the picture was taken (if it is present in the EXIF)

wasFlashFired :: Map ExifTag ExifValue -> Maybe Bool Source

Will return Just True if the flash was fired, Just False if it was not, and Nothing if the file does not contain the information.

formatAsFloatingPoint :: Int -> ExifValue -> String Source

Format the exif value as floating-point if it makes sense, otherwise use the default show implementation. The first parameter lets you specify how many digits after the comma to format in the result string. The special behaviour applies only for ExifRational and ExifRationalList.

getGpsDateTime :: Map ExifTag ExifValue -> Maybe LocalTime Source

Extract the GPS date time, if present in the picture.

parseGpsTime :: ExifValue -> Maybe TimeOfDay Source

read the GPS time from the gpsTimeStamp field.

The ExifValue type

data ExifValue Source

An exif value.

If you want a string describing the contents of the value, simply use show.

Constructors

ExifNumber !Int

An exif number. Originally it could have been short, int, signed or not.

ExifText !String

ASCII text.

ExifRational !Int !Int

A rational number (numerator, denominator). Sometimes we're used to it as rational (exposition time: 1/160), sometimes as float (exposure compensation, we rather think -0.75) show will display it as 1/160.

ExifNumberList ![Int]

List of numbers. Originally they could have been short, int, signed or not.

ExifRationalList ![(Int, Int)]

A list of rational numbers (numerator, denominator). Sometimes we're used to it as rational (exposition time: 1/160), sometimes as float (exposure compensation, we rather think -0.75) show will display it as 1/160.

ExifUndefined !ByteString

The undefined type in EXIF means that the contents are not specified and up to the manufacturer. In effect it's exactly a bytestring. Sometimes it's text with ASCII or UNICODE at the beginning, often it's binary in nature.

ExifUnknown !Word16 !Int !Int

Unknown exif value type. All EXIF 2.3 types are supported, it could be a newer file. The parameters are type, count then value

Instances

Most useful exif tags

exposureTime :: ExifTag Source

fnumber :: ExifTag Source

isoSpeedRatings :: ExifTag Source

dateTimeOriginal :: ExifTag Source

shutterSpeedValue :: ExifTag Source

apertureValue :: ExifTag Source

brightnessValue :: ExifTag Source

exposureBiasValue :: ExifTag Source

maxApertureValue :: ExifTag Source

flash :: ExifTag Source

focalLength :: ExifTag Source

userComment :: ExifTag Source

orientation :: ExifTag Source

make :: ExifTag Source

model :: ExifTag Source

software :: ExifTag Source

copyright :: ExifTag Source

digitalZoomRatio :: ExifTag Source

focalLengthIn35mmFilm :: ExifTag Source

artist :: ExifTag Source

GPS related exif tags

gpsVersionID :: ExifTag Source

gpsLatitudeRef :: ExifTag Source

gpsLatitude :: ExifTag Source

gpsLongitudeRef :: ExifTag Source

gpsLongitude :: ExifTag Source

gpsAltitudeRef :: ExifTag Source

gpsAltitude :: ExifTag Source

gpsTimeStamp :: ExifTag Source

gpsSatellites :: ExifTag Source

gpsStatus :: ExifTag Source

gpsMeasureMode :: ExifTag Source

gpsDop :: ExifTag Source

gpsSpeedRef :: ExifTag Source

gpsSpeed :: ExifTag Source

gpsTrackRef :: ExifTag Source

gpsTrack :: ExifTag Source

gpsImgDirectionRef :: ExifTag Source

gpsImgDirection :: ExifTag Source

gpsMapDatum :: ExifTag Source

gpsDestLatitudeRef :: ExifTag Source

gpsDestLatitude :: ExifTag Source

gpsDestLongitudeRef :: ExifTag Source

gpsDestLongitude :: ExifTag Source

gpsDestBearingRef :: ExifTag Source

gpsDestBearing :: ExifTag Source

gpsDestDistanceRef :: ExifTag Source

gpsDestDistance :: ExifTag Source

gpsProcessingMethod :: ExifTag Source

gpsAreaInformation :: ExifTag Source

gpsDateStamp :: ExifTag Source

gpsDifferential :: ExifTag Source

Less useful exif tags

exifVersion :: ExifTag Source

sensingMethod :: ExifTag Source

fileSource :: ExifTag Source

sceneType :: ExifTag Source

makerNote :: ExifTag Source

subjectDistance :: ExifTag Source

meteringMode :: ExifTag Source

lightSource :: ExifTag Source

exifImageWidth :: ExifTag Source

exifImageHeight :: ExifTag Source

relatedSoundFile :: ExifTag Source

focalPlaneXResolution :: ExifTag Source

focalPlaneYResolution :: ExifTag Source

focalPlaneResolutionUnit :: ExifTag Source

dateTimeDigitized :: ExifTag Source

componentConfiguration :: ExifTag Source

compressedBitsPerPixel :: ExifTag Source

exposureProgram :: ExifTag Source

spectralSensitivity :: ExifTag Source

oecf :: ExifTag Source

subjectArea :: ExifTag Source

subSecTime :: ExifTag Source

subSecTimeOriginal :: ExifTag Source

subSecTimeDigitized :: ExifTag Source

flashPixVersion :: ExifTag Source

colorSpace :: ExifTag Source

flashEnergy :: ExifTag Source

spatialFrequencyResponse :: ExifTag Source

subjectLocation :: ExifTag Source

exposureIndex :: ExifTag Source

cfaPattern :: ExifTag Source

customRendered :: ExifTag Source

exposureMode :: ExifTag Source

whiteBalance :: ExifTag Source

sceneCaptureType :: ExifTag Source

gainControl :: ExifTag Source

contrast :: ExifTag Source

saturation :: ExifTag Source

sharpness :: ExifTag Source

deviceSettingDescription :: ExifTag Source

subjectDistanceRange :: ExifTag Source

imageUniqueId :: ExifTag Source

exifInteroperabilityOffset :: ExifTag Source

imageDescription :: ExifTag Source

xResolution :: ExifTag Source

yResolution :: ExifTag Source

resolutionUnit :: ExifTag Source

dateTime :: ExifTag Source

whitePoint :: ExifTag Source

primaryChromaticities :: ExifTag Source

yCbCrPositioning :: ExifTag Source

yCbCrCoefficients :: ExifTag Source

referenceBlackWhite :: ExifTag Source

exifIfdOffset :: ExifTag Source

printImageMatching :: ExifTag Source

gpsTagOffset :: ExifTag Source

If you need to declare your own exif tags

data ExifTag Source

An exif tag. Normally you don't need to fiddle with this, except maybe if the library doesn't know the particular exif tag you're interested in. Rather check the list of supported exif tags, like exposureTime and so on.

Constructors

ExifTag 

Fields

tagLocation :: TagLocation

In which part of the JPEG file the exif tag was found

tagDesc :: Maybe String

Description of the exif tag (exposureTime, fnumber...) or if unknown, Nothing. This should be purely for debugging purposes, to compare tags use == on ExifTag or compare the tagKey.

tagKey :: Word16

Exif tag key, the number uniquely identifying this tag.

prettyPrinter :: ExifValue -> Text

A function that'll display nicely an exif value for that exif tag. For instance for the flash ExifTag, it'll say whether the flash was fired or not, if there was return light and so on.

Instances

data TagLocation Source

Location of the tag in the JPG file structure. Normally you don't need to fiddle with this, except maybe if the library doesn't know the particular exif tag you're interested in. Rather check the list of supported exif tags, like exposureTime and so on.

Constructors

ExifSubIFD 
IFD0 
GpsSubIFD 

Instances