Codec.BMP

Description

Reading and writing uncompressed 24 bit BMP files. We only handle Windows V3 file headers, but this is the most common.

To write a file do something like:

 do let rgba   = Data.ByteString.pack [some list of Word8s]
    let bmp    = packRGBA32ToBMP width height rgba
    writeBMP fileName bmp

To read a file do something like:

 do Right bmp  <- readBMP fileName
    let rgba   =  unpackBMPToRGBA32 bmp
    let (width, height) = bmpDimensions bmp
    ...

Synopsis

Documentation

data BMP Source

A BMP image. For an uncompressed image, the image data contains triples of BGR component values. Each line may also have zero pad values on the end, to bring them up to a multiple of 4 bytes in length.

Constructors

BMP
Fields bmpFileHeader :: FileHeader bmpBitmapInfo :: BitmapInfo bmpRawImageData :: ByteString

Instances

Show BMP

data FileHeader Source

BMP file header.

Constructors

FileHeader
Fields fileHeaderType :: Word16 Magic numbers 0x42 0x4d fileHeaderFileSize :: Word32 Size of the file, in bytes. fileHeaderReserved1 :: Word16 Reserved, must be zero. fileHeaderReserved2 :: Word16 Reserved, must be zero. fileHeaderOffset :: Word32 Offset in bytes to the start of the pixel data.

Instances

Show FileHeader
Binary FileHeader

data BitmapInfo Source

A wrapper for the bitmap info, in case we want to support other header types in the future.

Constructors

InfoV3 BitmapInfoV3

Instances

Show BitmapInfo
Binary BitmapInfo

data BitmapInfoV3 Source

Device Independent Bitmap (DIB) header for Windows V3.

Constructors

BitmapInfoV3

Fields

dib3Size :: Word32: Size of the image header, in bytes.
dib3Width :: Word32: Width of the image, in pixels.
dib3Height :: Word32: Height of the image, in pixels.
dib3Planes :: Word16: Number of color planes.
dib3BitCount :: Word16: Number of bits per pixel.
dib3Compression :: Word32: Image compression mode. 0 = uncompressed.
dib3ImageSize :: Word32: Size of raw image data.
dib3PelsPerMeterX :: Word32: Prefered resolution in pixels per meter, along the X axis.
dib3PelsPerMeterY :: Word32: Prefered resolution in pixels per meter, along the Y axis.
dib3ColorsUsed :: Word32: Number of color entries that are used.
dib3ColorsImportant :: Word32: Number of significant colors.

Instances

Show BitmapInfoV3
Binary BitmapInfoV3

data Error Source

Things that can go wrong when loading a BMP file.

Instances

Eq Error
Show Error

readBMP :: FilePath -> IO (Either Error BMP)Source

Wrapper for hGetBMP

writeBMP :: FilePath -> BMP -> IO ()Source

Wrapper for hPutBMP

hGetBMP :: Handle -> IO (Either Error BMP)Source

Get a BMP image from a file handle. The file is checked for problems and unsupported features when read. If there is anything wrong this gives an Error instead.

hPutBMP :: Handle -> BMP -> IO ()Source

Put a BMP image to a file handle. The size of the provided image data is checked against the given dimensions. If these don't match then error.

packRGBA32ToBMP Source

Arguments

:: Int	Width of image.
-> Int	Height of image.
-> ByteString	A string of RGBA component values. Must have length (`width * height * 4`)
-> BMP

Pack a string of RGBA component values into a BMP image. The alpha component is ignored. If the given dimensions don't match the input string then error.

unpackBMPToRGBA32 :: BMP -> ByteString Source

Unpack a BMP image to a string of RGBA component values. The alpha component is set to 255 for every pixel.

bmpDimensions :: BMP -> (Int, Int)Source

Get the width and height of an image. It's better to use this function than to access the headers directly.

ErrorReadOfFileHeaderFailed
ErrorReadOfImageHeaderFailed
ErrorReadOfImageDataFailed
ErrorBadMagic Word16
ErrorReservedFieldNotZero
ErrorDodgyFileHeaderFieldOffset Int
ErrorDodgyFileHeaderFieldFileSize Int
ErrorFileIsTruncated
ErrorUnhandledBitmapHeaderSize Int
ErrorUnhandledPlanesCount Int
ErrorUnhandledColorDepth Int
ErrorUnhandledCompressionMode Int
ErrorZeroImageSize
ErrorLacksWholeNumberOfLines