Class HeaderDecoder

java.lang.Object
jj2000.j2k.codestream.reader.HeaderDecoder
All Implemented Interfaces:
Markers, ProgressionType, StdEntropyCoderOptions

public class HeaderDecoder extends Object implements ProgressionType, Markers, StdEntropyCoderOptions
This class reads Main and Tile-part headers from the codestream. It is created by the run() method of the Decoder instance.

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:

  • Delimiting : SOC,SOT (read in FileBitstreamReaderAgent),SOD,EOC (read in FileBitstreamReaderAgent).
  • 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.

See Also:
  • Field Details

    • OPT_PREFIX

      public static final char OPT_PREFIX
      The prefix for header decoder options: 'H'
      See Also:
    • nTileParts

      public int[] nTileParts
      The number of tile parts per tile
    • SOD_FOUND

      public static final int SOD_FOUND
      Flag bit for SOD marker segment found
      See Also:
    • PPM_FOUND

      public static final int PPM_FOUND
      Flag bit for SOD marker segment found
      See Also:
    • PPT_FOUND

      public static final int PPT_FOUND
      Flag bit for SOD marker segment found
      See Also:
    • CRG_FOUND

      public static final int CRG_FOUND
      Flag bit for CRG marker segment found
      See Also:
    • mainHeadOff

      public int mainHeadOff
      The offset of the main header in the input stream
    • tileOfTileParts

      public Vector tileOfTileParts
      Vector containing info as to which tile each tilepart belong
  • Constructor Details

    • HeaderDecoder

      public HeaderDecoder(RandomAccessIO ehs, J2KImageReadParamJava j2krparam, HeaderInfo hi) throws IOException
      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.
      Parameters:
      ehs - The encoded header stream where marker segment are extracted.
      j2krparam - The parameter list of the decoder
      hi - The HeaderInfo holding information found in marker segments
      Throws:
      IOException - If an I/O error occurs while reading from the encoded header stream.
      EOFException - If the end of the encoded header stream is reached before getting all the data.
      CorruptedCodestreamException - If invalid data is found in the codestream main header.
  • Method Details

    • getMaxCompImgHeight

      public int getMaxCompImgHeight()
      Return the maximum height among all components
      Returns:
      Maximum component height
    • getMaxCompImgWidth

      public int getMaxCompImgWidth()
      Return the maximum width among all components
      Returns:
      Maximum component width
    • getImgWidth

      public final int getImgWidth()
      Returns the image width in the reference grid.
      Returns:
      The image width in the reference grid
    • getImgHeight

      public final int getImgHeight()
      Returns the image height in the reference grid.
      Returns:
      The image height in the reference grid
    • getImgULX

      public final int getImgULX()
      Return the horizontal upper-left coordinate of the image in the reference grid.
      Returns:
      The horizontal coordinate of the image origin.
    • getImgULY

      public final int getImgULY()
      Return the vertical upper-left coordinate of the image in the reference grid.
      Returns:
      The vertical coordinate of the image origin.
    • getNomTileWidth

      public final int getNomTileWidth()
      Returns the nominal width of the tiles in the reference grid.
      Returns:
      The nominal tile width, in the reference grid.
    • getNomTileHeight

      public final int getNomTileHeight()
      Returns the nominal width of the tiles in the reference grid.
      Returns:
      The nominal tile width, in the reference grid.
    • getTilingOrigin

      public final Point getTilingOrigin(Point co)
      Returns the tiling origin, referred to as '(Px,Py)' in the 'ImgData' interface.
      Parameters:
      co - If not null this object is used to return the information. If null a new one is created and returned.
      Returns:
      The coordinate of the tiling origin, in the canvas system, on the reference grid.
      See Also:
    • isOriginalSigned

      public final boolean isOriginalSigned(int c)
      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.
      Parameters:
      c - The index of the component
      Returns:
      True if the original image component was signed.
    • getOriginalBitDepth

      public final int getOriginalBitDepth(int c)
      Returns the original bitdepth of the specified component.
      Parameters:
      c - The index of the component
      Returns:
      The bitdepth of the component
    • getNumComps

      public final int getNumComps()
      Returns the number of components in the image.
      Returns:
      The number of components in the image.
    • getCompSubsX

      public final int getCompSubsX(int c)
      Returns the component sub-sampling factor, with respect to the reference grid, along the horizontal direction for the specified component.
      Parameters:
      c - The index of the component
      Returns:
      The component sub-sampling factor X-wise.
    • getCompSubsY

      public final int getCompSubsY(int c)
      Returns the component sub-sampling factor, with respect to the reference grid, along the vertical direction for the specified component.
      Parameters:
      c - The index of the component
      Returns:
      The component sub-sampling factor Y-wise.
    • createDequantizer

      public final Dequantizer createDequantizer(CBlkQuantDataSrcDec src, int[] rb, DecoderSpecs decSpec2)
      Returns the dequantizer parameters. Dequantizer parameters normally are the quantization step sizes, see DequantizerParams.
      Parameters:
      src - The source of data for the dequantizer.
      rb - The number of range bits for each component. Must be the number of range bits of the mixed components.
      decSpec2 - The DecoderSpecs instance after any image manipulation.
      Returns:
      The dequantizer
    • getCbULX

      public final int getCbULX()
      Returns the horizontal code-block partition origin.Allowable values are 0 and 1, nothing else.
    • getCbULY

      public final int getCbULY()
      Returns the vertical code-block partition origin. Allowable values are 0 and 1, nothing else.
    • getPPX

      public final int getPPX(int t, int c, int rl)
      Returns the precinct partition width for the specified tile-component and resolution level.
      Parameters:
      c - the component index
      t - the tile index
      rl - the resolution level
      Returns:
      The precinct partition width for the specified tile-component and resolution level
    • getPPY

      public final int getPPY(int t, int c, int rl)
      Returns the precinct partition height for the specified component, tile and resolution level.
      Parameters:
      c - the component
      t - the tile index
      rl - the resolution level
      Returns:
      The precinct partition height for the specified component, tile and resolution level
    • precinctPartitionUsed

      public final boolean precinctPartitionUsed()
      Returns the boolean used to know if the precinct partition is used
    • checkMarkerLength

      public void checkMarkerLength(DataInputStream ehs, String str) throws IOException
      Checks that the marker segment length is correct.
      Parameters:
      ehs - The encoded header stream
      str - The string identifying the marker, such as "SIZ marker"
      Throws:
      IOException - If an I/O error occurs
    • extractTilePartMarkSeg

      public void extractTilePartMarkSeg(short marker, RandomAccessIO ehs, int tileIdx, int tilePartIdx) throws IOException
      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.
      Parameters:
      marker - The marker to process
      ehs - The encoded header stream
      tileIdx - The index of the current tile
      tilePartIdx - The index of the current tile part
      Throws:
      IOException
    • readFoundTilePartMarkSeg

      public void readFoundTilePartMarkSeg(int tileIdx, int tpIdx) throws IOException
      Return the DecoderSpecs instance filled when reading the headers Retrieves and reads all marker segments previously found in the tile-part header.
      Parameters:
      tileIdx - The index of the current tile
      tpIdx - Index of the current tile-part
      Throws:
      IOException
    • getDecoderSpecs

      public DecoderSpecs getDecoderSpecs()
      Return the DecoderSpecs instance filled when reading the headers
      Returns:
      The DecoderSpecs of the decoder
    • createEntropyDecoder

      public EntropyDecoder createEntropyDecoder(CodedCBlkDataSrcDec src, J2KImageReadParamJava j2krparam)
      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.
      Parameters:
      src - The bit stream reader agent where to get code-block data from.
      j2krparam - The parameter list containing parameters applicable to the entropy decoder (other parameters can also be present).
      Returns:
      The entropy decoder
    • createROIDeScaler

      public ROIDeScaler createROIDeScaler(CBlkQuantDataSrcDec src, J2KImageReadParamJava j2krparam, DecoderSpecs decSpec2)
      Creates and returns the ROIDeScaler corresponding to the information read from the codestream header and with the special additional parameters from the parameter list.
      Parameters:
      src - The bit stream reader agent where to get code-block data from.
      j2krparam - The parameters applicable to the entropy decoder.
      Returns:
      The ROI descaler
    • resetHeaderMarkers

      public void resetHeaderMarkers()
      Method that resets members indicating which markers have already been found
    • toString

      public String toString()
      Print information about the current header.
      Overrides:
      toString in class Object
      Returns:
      Information in a String
    • getParameterInfo

      public static String[][] getParameterInfo()
      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.
      Returns:
      the options name, their synopsis and their explanation.
    • getNumTiles

      public int getNumTiles()
      Return the number of tiles in the image
      Returns:
      The number of tiles
    • getPackedPktHead

      public ByteArrayInputStream getPackedPktHead(int tile) throws IOException
      Return the packed packet headers for a given tile.
      Returns:
      An input stream containing the packed packet headers for a particular tile
      Throws:
      IOException - If an I/O error occurs while reading from the encoder header stream
    • setTileOfTileParts

      public void setTileOfTileParts(int tile)
      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.
      Parameters:
      tile - The tile number that the present tile part belongs to.
    • getNumFoundMarkSeg

      public int getNumFoundMarkSeg()
      Returns the number of found marker segments in the current header.
      Returns:
      The number of marker segments found in the current header.