Codec.Picture.Png.Streaming

A perfectly streaming PNG decoding library.

Decoding

decodePNG :: (MonadThrow m, MonadIO m) => ByteString m r -> m (DecodedPNG m (ByteString m r))

Decode a PNG from the given raw streaming ByteString. The result is header information followed by a stream of bytes that can be interpreted directly as pixels whose format depends on the image's colour type and bit depth.

Any remaining data after the end of the PNG image is returned untouched.

decodePNGComplete :: (MonadThrow m, MonadIO m) => ByteString m r -> m (DecodedPNG m r)

Decode a PNG from the given raw streaming ByteString. The result is header information followed by a stream of bytes that can be interpreted directly as pixels whose format depends on the image's colour type and bit depth.

If there is any more data after the end of the PNG image, an ExpectedEOF exception is thrown.

decodePNGFile :: MonadResource m => FilePath -> m (DecodedPNG m ())

Decode a PNG from the given file. The result is header information followed by a stream of bytes that can be interpreted directly as pixels whose format depends on the image's colour type and bit depth.

If there is any more data after the end of the PNG image, an ExpectedEOF exception is thrown.

decodeHeader :: MonadThrow m => ByteString m r -> m (Of HeaderData (ByteString m r))

Decode just the PNG header data from the given raw streaming ByteString, inspecting the minimum number of bytes from the input necessary to do so. The remaining bytes are returned also.

Types

data PNGDecodeError

The type of errors that might arise when decoding a PNG.

Constructors

IncorrectSignature

CRCMismatch

UnexpectedEOF

BadChunkSize ChunkType

UnexpectedChunk ChunkType

UnsupportedImageType

UnsupportedColourType

UnsupportedFilterType FilterType

ExpectedEOF

UnknownError String

Instances

Show PNGDecodeError

Exception PNGDecodeError

type DecodedPNG m r = Of HeaderData (ByteString m r)

A decoded PNG: header information followed by decoded pixel data whose format depends on the image's colour type and bit depth.

data HeaderData

Represents the header data of a PNG file in raw binary format.

Constructors

HeaderData

Fields

hdWidth :: Word32

hdHeight :: Word32

hdBitDepth :: BitDepth

hdColourType :: ColourType

hdCompressionMethod :: CompressionMethod

hdFilterMethod :: FilterMethod

hdInterlaceMethod :: InterlaceMethod

Instances

Show HeaderData

Misc

type ChunkType = ByteString

A chunk type, represented as a ByteString of length 4.

type BitDepth = Word8

A bit depth.

type ColourType = Word8

A colour type.

type CompressionMethod = Word8

A PNG compression method (distinct from the type in Zlib of the same name).

type FilterMethod = Word8

A PNG filtering method.

type FilterType = Word8

A PNG filter type, for filter method 0.

type InterlaceMethod = Word8

A PNG interlacing method.

isColourTypeSupported :: ColourType -> Bool

Is the given PNG image colour type supported? Currently we only support non-indexed colour types.

isCompressionMethodSupported :: CompressionMethod -> Bool

Is the given PNG compression method supported? Currently we only support method 0.

isFilterMethodSupported :: FilterMethod -> Bool

Is the given PNG filter method supported? Currently we only support method 0.

isInterlaceMethodSupported :: InterlaceMethod -> Bool

Is the given PNG interlace method supported? Currently only the null interlace method (no interlacing) is supported.