GHC 10.0.0.20260917 · lts/ghc-10.0.x · 8fef28d · 2026-11-02
ModuleJuicyPixels-3.3.9Haskell2010
Low level png module, you should import Codec.Picture.Png.Internal instead.
Generic header used in PNG images.
PngIHdrwidth :: !Word32Image width in number of pixel
height :: !Word32Image height in number of pixel
bitDepth :: !Word8Number of bit per sample
colourType :: !PngImageTypeKind of png image (greyscale, true color, indexed...)
compressionMethod :: !Word8Compression method used
filterMethod :: !Word8Must be 0
interlaceMethod :: !PngInterlaceMethodIf the image is interlaced (for progressive rendering)
The pixels value should be : +---+---+ | c | b | +---+---+ | a | x | +---+---+ x being the current filtered pixel
FilterNoneFilt(x) = Orig(x), Recon(x) = Filt(x)
FilterSubFilt(x) = Orig(x) - Orig(a), Recon(x) = Filt(x) + Recon(a)
FilterUpFilt(x) = Orig(x) - Orig(b), Recon(x) = Filt(x) + Recon(b)
FilterAverageFilt(x) = Orig(x) - floor((Orig(a) + Orig(b)) / 2), Recon(x) = Filt(x) + floor((Recon(a) + Recon(b)) / 2)
FilterPaethFilt(x) = Orig(x) - PaethPredictor(Orig(a), Orig(b), Orig(c)), Recon(x) = Filt(x) + PaethPredictor(Recon(a), Recon(b), Recon(c))
Different known interlace methods for PNG image
PngNoInterlaceNo interlacing, basic data ordering, line by line from left to right.
PngInterlaceAdam7Use the Adam7 ordering, see adam7Reordering
Enum PngInterlaceMethodDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeShow PngInterlaceMethodDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeBinary PngInterlaceMethodDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypePalette with indices beginning at 0 to elemcount - 1
What kind of information is encoded in the IDAT section of the PngFile
Show PngImageTypeDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeBinary PngImageTypeDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeBinary PngPhysicalDimensionDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypePngUnitUnknown0 value
PngUnitMeter1 value
Show APngAnimationControlDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeEncoded in a Word8
APngDisposeNoneNo disposal is done on this frame before rendering the next; the contents of the output buffer are left as is. Has Value 0
APngDisposeBackgroundThe frame's region of the output buffer is to be cleared to fully transparent black before rendering the next frame. Has Value 1
APngDisposePreviousthe frame's region of the output buffer is to be reverted to the previous contents before rendering the next frame. Has Value 2
Show APngFrameDisposalDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeEncoded in a Word8
APngBlendSourceOverwrite output buffer. has value '0'
APngBlendOverAlpha blend to the output buffer. Has value '1'
Show APngBlendOpDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeAPngFrameControlframeSequenceNum :: !Word32Starting from 0
frameWidth :: !Word32Width of the following frame
frameHeight :: !Word32Height of the following frame
frameLeft :: !Word32frameTop :: !Word32frameDelayNumerator :: !Word16frameDelayDenuminator :: !Word16frameDisposal :: !APngFrameDisposalframeBlending :: !APngBlendOpShow APngFrameControlDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeParse a palette from a png chunk.
Compute the CRC of a raw buffer, as described in annex D of the PNG specification.
Signature signalling that the following data will be a png image in the png bit stream
Signature for the header chunk of png (must be the first)
Signature for a palette chunk in the pgn file. Must occure before iDAT.
Signature for a data chuck (with image parts in it)
Signature for the last chunk of a png image, telling the end.
Value used to identify a png chunk, must be 4 bytes long.
Raw parsed image which need to be decoded.
Binary PngRawImageDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypePNG chunk representing some extra information found in the parsed file.
PngChunkpngChunkData :: ByteStringThe raw data inside the chunk
pngChunkSignature :: ChunkSignatureThe name of the chunk.
Data structure during real png loading/parsing
Binary PngRawChunkDefined in JuicyPixels-3.3.9 · Codec.Picture.Png.Internal.TypeLow level access to PNG information