HeaderDecoder Class

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.

       <p>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:

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

       <ol><li>All marker segments are buffered and their corresponding flag is
       activated (extractMainMarkSeg and extractTilePartMarkSeg methods).</li><li>Buffered marker segment are analyzed in a logical way and
       specifications are stored in appropriate member of DecoderSpecs instance
       (readFoundMainMarkSeg and readFoundTilePartMarkSeg methods).</li></ol></p><p>Whenever a marker segment is not recognized a warning message is
       displayed and its length parameter is used to skip it.</p><p>The information found in this header is stored in HeaderInfo and
       DecoderSpecs instances.</p>

Inheritance

object

HeaderDecoder

Namespace: CSJ2K.j2k.codestream.reader

Assembly: C1.WPF.ReportViewer.4.6.2.dll

Syntax

public class HeaderDecoder

Public Class HeaderDecoder

Constructors

Name	Description
HeaderDecoder(RandomAccessIO, ParameterList, HeaderInfo)	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.

Fields

Name	Description
CRG_FOUND	Flag bit for CRG marker segment found
OPT_PREFIX	The prefix for header decoder options: 'H'
PPM_FOUND	Flag bit for SOD marker segment found
PPT_FOUND	Flag bit for SOD marker segment found
SOD_FOUND	Flag bit for SOD marker segment found
mainHeadOff	The offset of the main header in the input stream
nTileParts	The number of tile parts in each tile

Properties

Name	Description
CbULX	Returns the horizontal code-block partition origin.Allowable values are 0 and 1, nothing else.
CbULY	Returns the vertical code-block partition origin. Allowable values are 0 and 1, nothing else.
DecoderSpecs	Return the DecoderSpecs instance filled when reading the headers
ImgHeight	Returns the image height in the reference grid.
ImgULX	Return the horizontal upper-left coordinate of the image in the reference grid.
ImgULY	Return the vertical upper-left coordinate of the image in the reference grid.
ImgWidth	Returns the image width in the reference grid.
MaxCompImgHeight	Return the maximum height among all components
MaxCompImgWidth	Return the maximum width among all components
NomTileHeight	Returns the nominal width of the tiles in the reference grid.
NomTileWidth	Returns the nominal width of the tiles in the reference grid.
NumComps	Returns the number of components in the image.
NumFoundMarkSeg	Returns the number of found marker segments in the current header.
NumTiles	Return the number of tiles in the image
ParameterInfo	Returns the parameters that are used in this class. It returns a 2D String array. Each of the 1D arrays is for a different option, and they have 3 elements. The first element is the option name, the second one is the synopsis and the third one is a long description of what the parameter is. The synopsis or description may be 'null', in which case it is assumed that there is no synopsis or description of the option, respectively.
TileOfTileParts	Sets the tile of each tile part in order. This information is needed for identifying which packet header belongs to which tile when using the PPM marker.

Methods

Name	Description
ToString()	Print information about the current header.
checkMarkerLength(BinaryReader, string)	Checks that the marker segment length is correct.
createChannelDefinitionMapper(BlkImgDataSrc, ColorSpace)	Creates and returns the ChannelDefinitonMapper which maps the input channels to the channel definition for the appropriate colorspace.
createColorSpaceMapper(BlkImgDataSrc, ColorSpace)	Creates and returns the EnumeratedColorSpaceMapper corresponding to the information read from the JP2 image file via the ColorSpace parameter.
createDequantizer(CBlkQuantDataSrcDec, int[], DecoderSpecs)	Returns the dequantizer parameters. Dequantizer parameters normally are the quantization step sizes, see DequantizerParams.
createEntropyDecoder(CodedCBlkDataSrcDec, ParameterList)	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, ColorSpace)	Creates and returns the PalettizedColorSpaceMapper which uses the input samples as indicies into a sample palette to construct the output.
createROIDeScaler(CBlkQuantDataSrcDec, ParameterList, DecoderSpecs)	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, ColorSpace)	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, RandomAccessIO, int, int)	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)	Returns the component sub-sampling factor, with respect to the reference grid, along the horizontal direction for the specified component.
getCompSubsY(int)	Returns the component sub-sampling factor, with respect to the reference grid, along the vertical direction for the specified component.
getOriginalBitDepth(int)	Returns the original bitdepth of the specified component.
getPPX(int, int, int)	Returns the precinct partition width for the specified tile-component and resolution level.
getPPY(int, int, int)	Returns the precinct partition height for the specified tile-component and resolution level.
getPackedPktHead(int)	Return the packed packet headers for a given tile.
getTilingOrigin(Coord)	Returns the tiling origin, referred to as '(Px,Py)' in the 'ImgData' interface.
isOriginalSigned(int)	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()	Returns the boolean used to know if the precinct partition is used
readFoundTilePartMarkSeg(int, int)	Retrieves and reads all marker segments previously found in the tile-part header.
resetHeaderMarkers()	Method that resets members indicating which markers have already been found