C# Class CSJ2K.j2k.codestream.reader.HeaderDecoder

This class reads main and tile-part headers from the codestream given a RandomAccessIO instance located at the beginning of the codestream (i.e just before the SOC marker) or at the beginning of a tile-part (i.e. just before a SOT marker segment) respectively.

A marker segment includes a marker and eventually marker segment parameters. It is designed by the three letters code of the marker associated with the marker segment. JPEG 2000 part 1 defines 6 types of markers segments:

Delimiting : SOC, SOT, SOD, EOC
Fixed information: SIZ.
Functional: COD, COC, RGN, QCD, QCC,POC.
In bit-stream: SOP, EPH.
Pointer: TLM, PLM, PLT, PPM, PPT.
Informational: CRG, COM.

The main header is read when the constructor is called whereas tile-part headers are read when the FileBitstreamReaderAgent instance is created. The reading is done in 2 passes:

All marker segments are buffered and their corresponding flag is activated (extractMainMarkSeg and extractTilePartMarkSeg methods).
Buffered marker segment are analyzed in a logical way and specifications are stored in appropriate member of DecoderSpecs instance (readFoundMainMarkSeg and readFoundTilePartMarkSeg methods).

Whenever a marker segment is not recognized a warning message is displayed and its length parameter is used to skip it.

The information found in this header is stored in HeaderInfo and DecoderSpecs instances.

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Public Properties

Property	Type	Description
mainHeadOff	int
nTileParts	int[]

Public Methods

Method	Description
HeaderDecoder ( RandomAccessIO ehs, CSJ2K.j2k.util.ParameterList pl, HeaderInfo hi ) : System	Creates a HeaderDecoder instance and read in two passes the main header of the codestream. The first and last marker segments shall be respectively SOC and SOT.
ToString ( ) : System.String	Print information about the current header.
checkMarkerLength ( System ehs, System str ) : void	Checks that the marker segment length is correct.
createChannelDefinitionMapper ( BlkImgDataSrc src, CSJ2K csMap ) : BlkImgDataSrc	Creates and returns the ChannelDefinitonMapper which maps the input channels to the channel definition for the appropriate colorspace.
createColorSpaceMapper ( BlkImgDataSrc src, CSJ2K csMap ) : BlkImgDataSrc	Creates and returns the EnumeratedColorSpaceMapper corresponding to the information read from the JP2 image file via the ColorSpace parameter.
createDequantizer ( CBlkQuantDataSrcDec src, int rb, DecoderSpecs decSpec2 ) : CSJ2K.j2k.quantization.dequantizer.Dequantizer	Returns the dequantizer parameters. Dequantizer parameters normally are the quantization step sizes, see DequantizerParams.
createEntropyDecoder ( CodedCBlkDataSrcDec src, CSJ2K.j2k.util.ParameterList pl ) : CSJ2K.j2k.entropy.decoder.EntropyDecoder	Creates and returns the entropy decoder corresponding to the information read from the codestream header and with the special additional parameters from the parameter list.
createPalettizedColorSpaceMapper ( BlkImgDataSrc src, CSJ2K csMap ) : BlkImgDataSrc	Creates and returns the PalettizedColorSpaceMapper which uses the input samples as indicies into a sample palette to construct the output.
createROIDeScaler ( CBlkQuantDataSrcDec src, CSJ2K.j2k.util.ParameterList pl, DecoderSpecs decSpec2 ) : CSJ2K.j2k.roi.ROIDeScaler	Creates and returns the ROIDeScaler corresponding to the information read from the codestream header and with the special additional parameters from the parameter list.
createResampler ( BlkImgDataSrc src, CSJ2K csMap ) : BlkImgDataSrc	Creates and returns the Resampler which converts the input source to one in which all channels have the same number of samples. This is required for colorspace conversions.
extractTilePartMarkSeg ( short marker, RandomAccessIO ehs, int tileIdx, int tilePartIdx ) : void	This method extracts a marker segment in a tile-part header and stores it into a byte buffer for the second pass. The marker is first recognized, then its flag is activated and, finally, its content is buffered in an element of byte arrays accessible thanks to a hashTable. If a marker segment is not recognized, it prints a warning and skip it according to its length.
getCompSubsX ( int c ) : int	Returns the component sub-sampling factor, with respect to the reference grid, along the horizontal direction for the specified component.
getCompSubsY ( int c ) : int	Returns the component sub-sampling factor, with respect to the reference grid, along the vertical direction for the specified component.
getOriginalBitDepth ( int c ) : int	Returns the original bitdepth of the specified component.
getPPX ( int t, int c, int rl ) : int	Returns the precinct partition width for the specified tile-component and resolution level.
getPPY ( int t, int c, int rl ) : int	Returns the precinct partition height for the specified tile-component and resolution level.
getPackedPktHead ( int tile ) : System.IO.MemoryStream	Return the packed packet headers for a given tile.
getTilingOrigin ( Coord co ) : Coord	Returns the tiling origin, referred to as '(Px,Py)' in the 'ImgData' interface.
isOriginalSigned ( int c ) : bool	Returns true if the original data of the specified component was signed. If the data was not signed a level shift has to be applied at the end of the decompression chain.
precinctPartitionUsed ( ) : bool	Returns the boolean used to know if the precinct partition is used
readFoundTilePartMarkSeg ( int tileIdx, int tpIdx ) : void	Retrieves and reads all marker segments previously found in the tile-part header.
resetHeaderMarkers ( ) : void	Method that resets members indicating which markers have already been found

Private Methods

Method	Description
extractMainMarkSeg ( short marker, RandomAccessIO ehs ) : void	This method extract a marker segment from the main header and stores it into a byte buffer for the second pass. The marker segment is first identified. Then its flag is activated. Finally, its content is buffered into a byte array stored in an hashTable. If the marker is not recognized, it prints a warning and skips it according to its length. SIZ marker segment shall be the first encountered marker segment.
readCOC ( System ehs, bool mainh, int tileIdx, int tpIdx ) : void	Reads the COC marker segment and realigns the codestream where the next marker should be found.
readCOD ( System ehs, bool mainh, int tileIdx, int tpIdx ) : void	Reads a COD marker segment and realigns the codestream where the next marker should be found.
readCOM ( System ehs, bool mainh, int tileIdx, int comIdx ) : void	Reads a COM marker segments and realigns the bit stream at the point where the next marker segment should be found. COM is an informational marker segment that allows to include unstructured data in the main and tile-part headers.
readCRG ( System ehs ) : void	Reads a CRG marker segment and checks its length. CRG is an informational marker segment that allows specific registration of components with respect to each other.
readFilter ( System ehs, int filtIdx ) : CSJ2K.j2k.wavelet.synthesis.SynWTFilter	Reads a wavelet filter from the codestream and returns the filter object that implements it.
readFoundMainMarkSeg ( ) : void	Retrieves and reads all marker segments found in the main header during the first pass.
readPLM ( System ehs ) : void	Reads PLM marker segment and realigns the codestream where the next marker should be found. Informations stored in these fields are currently not taken into account.
readPLTFields ( System ehs ) : void	Reads the PLT fields and realigns the codestream where the next marker should be found. Informations stored in these fields are currently NOT taken into account.
readPOC ( System ehs, bool mainh, int t, int tpIdx ) : void	Reads the POC marker segment and realigns the codestream where the next marker should be found.
readPPM ( System ehs ) : void	Reads the PPM marker segment of the main header.
readPPT ( System ehs, int tile, int tpIdx ) : void	Reads the PPT marker segment of the main header.
readQCC ( System ehs, bool mainh, int tileIdx, int tpIdx ) : void	Reads a QCC marker segment and realigns the codestream at the point where the next marker should be found. QCC is a functional marker segment that describes the quantization of one component.
readQCD ( System ehs, bool mainh, int tileIdx, int tpIdx ) : void	Reads a QCD marker segment and realigns the codestream at the point where the next marker should be found. QCD is a functional marker segment that describes the quantization default.
readRGN ( System ehs, bool mainh, int tileIdx, int tpIdx ) : void	Reads the RGN marker segment of the codestream header. May be used in tile or main header. If used in main header, it refers to the maxshift value of a component in all tiles. When used in tile header, only the particular tile-component is affected.
readSIZ ( System ehs ) : void	Reads the SIZ marker segment and realigns the codestream at the point where the next marker segment should be found. SIZ is a fixed information marker segment containing informations about image and tile sizes. It is required in the main header immediately after SOC.
readTLM ( System ehs ) : void	Reads TLM marker segment and realigns the codestream where the next marker should be found. Informations stored in these fields are currently NOT taken into account.

Method Details

HeaderDecoder() public method

Creates a HeaderDecoder instance and read in two passes the main header of the codestream. The first and last marker segments shall be respectively SOC and SOT.

If an I/O error occurs while reading from the /// encoded header stream. /// If the end of the encoded header stream is /// reached before getting all the data. /// If invalid data is found in the /// codestream main header. /// ///

public HeaderDecoder ( RandomAccessIO ehs, CSJ2K.j2k.util.ParameterList pl, HeaderInfo hi ) : System
ehs	RandomAccessIO	The encoded header stream where marker segments are /// extracted. /// ///
pl	CSJ2K.j2k.util.ParameterList	The ParameterList object of the decoder /// ///
hi	CSJ2K.j2k.codestream.HeaderInfo	The HeaderInfo holding information found in marker segments /// ///
return	System

ToString() public method

Print information about the current header.

public ToString ( ) : System.String
return	System.String

checkMarkerLength() public method

Checks that the marker segment length is correct.

If an I/O error occurs /// ///

public checkMarkerLength ( System ehs, System str ) : void
ehs	System	The encoded header stream /// ///
str	System	The string identifying the marker, such as "SIZ marker" /// ///
return	void

createChannelDefinitionMapper() public method

Creates and returns the ChannelDefinitonMapper which maps the input channels to the channel definition for the appropriate colorspace.

image access exception /// if image contains a bad colorspace box /// ///

public createChannelDefinitionMapper ( BlkImgDataSrc src, CSJ2K csMap ) : BlkImgDataSrc
src	BlkImgDataSrc	The bit stream reader agent where to get code-block /// data from. ///
csMap	CSJ2K	provides color space information from the image file /// ///
return	BlkImgDataSrc

createColorSpaceMapper() public method

Creates and returns the EnumeratedColorSpaceMapper corresponding to the information read from the JP2 image file via the ColorSpace parameter.

image access exception /// if image contains a bad icc profile /// if image contains a bad colorspace box /// ///

public createColorSpaceMapper ( BlkImgDataSrc src, CSJ2K csMap ) : BlkImgDataSrc
src	BlkImgDataSrc	The bit stream reader agent where to get code-block /// data from. ///
csMap	CSJ2K	provides color space information from the image file /// ///
return	BlkImgDataSrc

createDequantizer() public method

Returns the dequantizer parameters. Dequantizer parameters normally are the quantization step sizes, see DequantizerParams.

public createDequantizer ( CBlkQuantDataSrcDec src, int rb, DecoderSpecs decSpec2 ) : CSJ2K.j2k.quantization.dequantizer.Dequantizer
src	CBlkQuantDataSrcDec	The source of data for the dequantizer. /// ///
rb	int	The number of range bits for each component. Must be /// the number of range bits of the mixed components. /// ///
decSpec2	CSJ2K.j2k.decoder.DecoderSpecs	The DecoderSpecs instance after any image manipulation. /// ///
return	CSJ2K.j2k.quantization.dequantizer.Dequantizer

createEntropyDecoder() public method

Creates and returns the entropy decoder corresponding to the information read from the codestream header and with the special additional parameters from the parameter list.

public createEntropyDecoder ( CodedCBlkDataSrcDec src, CSJ2K.j2k.util.ParameterList pl ) : CSJ2K.j2k.entropy.decoder.EntropyDecoder
src	CodedCBlkDataSrcDec	The bit stream reader agent where to get code-block data /// from. /// ///
pl	CSJ2K.j2k.util.ParameterList	The parameter list containing parameters applicable to the /// entropy decoder (other parameters can also be present). /// ///
return	CSJ2K.j2k.entropy.decoder.EntropyDecoder

createPalettizedColorSpaceMapper() public method

Creates and returns the PalettizedColorSpaceMapper which uses the input samples as indicies into a sample palette to construct the output.

image access exception /// if image contains a bad colorspace box /// ///

public createPalettizedColorSpaceMapper ( BlkImgDataSrc src, CSJ2K csMap ) : BlkImgDataSrc
src	BlkImgDataSrc	The bit stream reader agent where to get code-block /// data from. ///
csMap	CSJ2K	provides color space information from the image file /// ///
return	BlkImgDataSrc

createROIDeScaler() public method

Creates and returns the ROIDeScaler corresponding to the information read from the codestream header and with the special additional parameters from the parameter list.

public createROIDeScaler ( CBlkQuantDataSrcDec src, CSJ2K.j2k.util.ParameterList pl, DecoderSpecs decSpec2 ) : CSJ2K.j2k.roi.ROIDeScaler
src	CBlkQuantDataSrcDec	The bit stream reader agent where to get code-block data /// from. /// ///
pl	CSJ2K.j2k.util.ParameterList	The parameter list containing parameters applicable to the /// entropy decoder (other parameters can also be present). /// ///
decSpec2	CSJ2K.j2k.decoder.DecoderSpecs	The DecoderSpecs instance after any image manipulation. /// ///
return	CSJ2K.j2k.roi.ROIDeScaler

createResampler() public method

Creates and returns the Resampler which converts the input source to one in which all channels have the same number of samples. This is required for colorspace conversions.

image access exception /// if image contains a bad colorspace box /// ///

public createResampler ( BlkImgDataSrc src, CSJ2K csMap ) : BlkImgDataSrc
src	BlkImgDataSrc	The bit stream reader agent where to get code-block /// data from. ///
csMap	CSJ2K	provides color space information from the image file /// ///
return	BlkImgDataSrc

extractTilePartMarkSeg() public method

This method extracts a marker segment in a tile-part header and stores it into a byte buffer for the second pass. The marker is first recognized, then its flag is activated and, finally, its content is buffered in an element of byte arrays accessible thanks to a hashTable. If a marker segment is not recognized, it prints a warning and skip it according to its length.

public extractTilePartMarkSeg ( short marker, RandomAccessIO ehs, int tileIdx, int tilePartIdx ) : void
marker	short	The marker to process /// ///
ehs	RandomAccessIO	The encoded header stream /// ///
tileIdx	int	The index of the current tile /// ///
tilePartIdx	int	The index of the current tile part /// ///
return	void

getCompSubsX() public method

Returns the component sub-sampling factor, with respect to the reference grid, along the horizontal direction for the specified component.

public getCompSubsX ( int c ) : int
c	int	The index of the component /// ///
return	int

getCompSubsY() public method

Returns the component sub-sampling factor, with respect to the reference grid, along the vertical direction for the specified component.

public getCompSubsY ( int c ) : int
c	int	The index of the component /// ///
return	int

getOriginalBitDepth() public method

Returns the original bitdepth of the specified component.

public getOriginalBitDepth ( int c ) : int
c	int	The index of the component /// ///
return	int

getPPX() public method

Returns the precinct partition width for the specified tile-component and resolution level.

public getPPX ( int t, int c, int rl ) : int
t	int	the tile index /// ///
c	int	the component index /// ///
rl	int	the resolution level /// ///
return	int

getPPY() public method

Returns the precinct partition height for the specified tile-component and resolution level.

public getPPY ( int t, int c, int rl ) : int
t	int	the tile index /// ///
c	int	the component index /// ///
rl	int	the resolution level /// ///
return	int

getPackedPktHead() public method

Return the packed packet headers for a given tile.

If an I/O error occurs while reading from the /// encoder header stream /// ///

public getPackedPktHead ( int tile ) : System.IO.MemoryStream
tile	int
return	System.IO.MemoryStream

getTilingOrigin() public method

Returns the tiling origin, referred to as '(Px,Py)' in the 'ImgData' interface.

public getTilingOrigin ( Coord co ) : Coord
co	Coord	If not null this object is used to return the information. If /// null a new one is created and returned. /// ///
return	Coord

isOriginalSigned() public method

Returns true if the original data of the specified component was signed. If the data was not signed a level shift has to be applied at the end of the decompression chain.

public isOriginalSigned ( int c ) : bool
c	int	The index of the component /// ///
return	bool

precinctPartitionUsed() public method

Returns the boolean used to know if the precinct partition is used

public precinctPartitionUsed ( ) : bool
return	bool

readFoundTilePartMarkSeg() public method

Retrieves and reads all marker segments previously found in the tile-part header.

public readFoundTilePartMarkSeg ( int tileIdx, int tpIdx ) : void
tileIdx	int	The index of the current tile /// ///
tpIdx	int	Index of the current tile-part /// ///
return	void

resetHeaderMarkers() public method

Method that resets members indicating which markers have already been found

public resetHeaderMarkers ( ) : void
return	void

Property Details

mainHeadOff public_oe property

The offset of the main header in the input stream

public int mainHeadOff
return	int

nTileParts public_oe property

The number of tile parts in each tile

public int[] nTileParts
return	int[]