ucar.jpeg.jj2000.j2k.image.input

Class ImgReaderPGX

java.lang.Object

ucar.jpeg.jj2000.j2k.image.input.ImgReader

ucar.jpeg.jj2000.j2k.image.input.ImgReaderPGX

All Implemented Interfaces:

BlkImgDataSrc, ImgData, EndianType

public class ImgReaderPGX
extends ImgReader
implements EndianType

This class extends the ImgReader abstract class for reading PGX files. PGX is a custom monochrome file format invented specifically to simplify the use of JPEG 2000 with images of different bit-depths in the range 1 to 31 bits per pixel.

The file consists of a one line text header followed by the data.

Header: "PG"+ ws +<endianess>+ ws +[sign]+ws + <bit-depth>+" "+<width>+" "+<height>+'\n'

where:

• ws (white-spaces) is any combination of characters ' ' and '\t'.
• endianess equals "LM" or "ML"(resp. little-endian or big-endian)
• sign equals "+" or "-" (resp. unsigned or signed). If omited, values are supposed to be unsigned.
• bit-depth that can be any number between 1 and 31.
• width and height are the image dimensions (in pixels).

Data: The image binary values appear one after the other (in raster order) immediately after the last header character ('\n') and are byte-aligned (they are packed into 1,2 or 4 bytes per sample, depending upon the bit-depth value).

If the data is unisigned, level shifting is applied subtracting 2^(bitdepth - 1)

Since it is not possible to know the input file byte-ordering before reading its header, this class can not be construct from a RandomAccessIO. So, the constructor has to open first the input file, to read only its header, and then it can create the appropriate BufferedRandomAccessFile (Big-Endian or Little-Endian byte-ordering).

NOTE: This class is not thread safe, for reasons of internal buffering.

See Also:

jj2000.j2k.image.ImgData, RandomAccessIO, BufferedRandomAccessFile, BEBufferedRandomAccessFile

Field Summary

Fields inherited from class ucar.jpeg.jj2000.j2k.image.input.ImgReader

h, nc, w

Fields inherited from interface ucar.jpeg.jj2000.j2k.io.EndianType

BIG_ENDIAN, LITTLE_ENDIAN

Constructor Summary

Constructors

Constructor and Description
ImgReaderPGX(File in) Creates a new PGX file reader from the specified File object.
ImgReaderPGX(String inName) Creates a new PGX file reader from the specified file name.

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Closes the underlying RandomAccessIO from where the image data is being read.
DataBlk	getCompData(DataBlk blk, int c) Returns, in the blk argument, a block of image data containing the specifed rectangular area, in the specified component.
int	getFixedPoint(int c) Returns the position of the fixed point in the specified component (i.e.
DataBlk	getInternCompData(DataBlk blk, int c) Returns, in the blk argument, the block of image data containing the specifed rectangular area, in the specified component.
int	getNomRangeBits(int c) Returns the number of bits corresponding to the nominal range of the data in the specified component.
boolean	isOrigSigned(int c) Returns true if the data read was originally signed in the specified component, false if not.
String	toString() Returns a string of information about the object, more than 1 line long.

Methods inherited from class ucar.jpeg.jj2000.j2k.image.input.ImgReader

getCompImgHeight, getCompImgWidth, getCompSubsX, getCompSubsY, getCompULX, getCompULY, getImgHeight, getImgULX, getImgULY, getImgWidth, getNomTileHeight, getNomTileWidth, getNumComps, getNumTiles, getNumTiles, getTile, getTileCompHeight, getTileCompWidth, getTileHeight, getTileIdx, getTilePartULX, getTilePartULY, getTileWidth, nextTile, setTile

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ImgReaderPGX

public ImgReaderPGX(File in)
             throws IOException

Creates a new PGX file reader from the specified File object.

Parameters:

in - The input file as File object.

Throws:

IOException - If an I/O error occurs.

ImgReaderPGX

public ImgReaderPGX(String inName)
             throws IOException

Creates a new PGX file reader from the specified file name.

Parameters:

inName - The input file name.

Throws:

IOException

Method Detail

close

public void close()
           throws IOException

Closes the underlying RandomAccessIO from where the image data is being read. No operations are possible after a call to this method.

Specified by:

close in class ImgReader

Throws:

IOException - If an I/O error occurs.

getNomRangeBits

public int getNomRangeBits(int c)

Returns the number of bits corresponding to the nominal range of the data in the specified component. This is the value of bitDepth which is read in the PGX file header.

If this number is b then the nominal range is between -2^(b-1) and 2^(b-1)-1, for originally signed or unsigned data (unsigned data is level shifted to have a nominal average of 0).

Specified by:

getNomRangeBits in interface ImgData

Parameters:

c - The index of the component.

Returns:

The number of bits corresponding to the nominal range of the data.

getFixedPoint

public int getFixedPoint(int c)

Returns the position of the fixed point in the specified component (i.e. the number of fractional bits), which is always 0 for this ImgReader.

Specified by:

getFixedPoint in interface BlkImgDataSrc

Parameters:

c - The index of the component.

Returns:

The position of the fixed-point (i.e. the number of fractional bits). Always 0 for this ImgReader.

getInternCompData

public DataBlk getInternCompData(DataBlk blk,
                        int c)

Returns, in the blk argument, the block of image data containing the specifed rectangular area, in the specified component. The data is returned, as a reference to the internal data, if any, instead of as a copy, therefore the returned data should not be modified.

After being read the coefficients are level shifted by subtracting 2^(nominal bit range - 1)

The rectangular area to return is specified by the 'ulx', 'uly', 'w' and 'h' members of the 'blk' argument, relative to the current tile. These members are not modified by this method. The 'offset' and 'scanw' of the returned data can be arbitrary. See the 'DataBlk' class.

If the data array in blk is null, then a new one is created if necessary. The implementation of this interface may choose to return the same array or a new one, depending on what is more efficient. Therefore, the data array in blk prior to the method call should not be considered to contain the returned data, a new array may have been created. Instead, get the array from blk after the method has returned.

The returned data always has its 'progressive' attribute unset (i.e. false).

When an I/O exception is encountered the JJ2KExceptionHandler is used. The exception is passed to its handleException method. The action that is taken depends on the action that has been registered in JJ2KExceptionHandler. See JJ2KExceptionHandler for details.

Specified by:

getInternCompData in interface BlkImgDataSrc

Parameters:

blk - Its coordinates and dimensions specify the area to return. Some fields in this object are modified to return the data.

c - The index of the component from which to get the data. Only 0 is valid.

Returns:

The requested DataBlk

See Also:

getCompData(ucar.jpeg.jj2000.j2k.image.DataBlk, int), JJ2KExceptionHandler

getCompData

public DataBlk getCompData(DataBlk blk,
                  int c)

Returns, in the blk argument, a block of image data containing the specifed rectangular area, in the specified component. The data is returned, as a copy of the internal data, therefore the returned data can be modified "in place".

After being read the coefficients are level shifted by subtracting 2^(nominal bit range - 1)

The rectangular area to return is specified by the 'ulx', 'uly', 'w' and 'h' members of the 'blk' argument, relative to the current tile. These members are not modified by this method. The 'offset' of the returned data is 0, and the 'scanw' is the same as the block's width. See the 'DataBlk' class.

If the data array in 'blk' is 'null', then a new one is created. If the data array is not 'null' then it is reused, and it must be large enough to contain the block's data. Otherwise an 'ArrayStoreException' or an 'IndexOutOfBoundsException' is thrown by the Java system.

The returned data has its 'progressive' attribute unset (i.e. false).

This method just calls 'getInternCompData(blk,c)'.

When an I/O exception is encountered the JJ2KExceptionHandler is used. The exception is passed to its handleException method. The action that is taken depends on the action that has been registered in JJ2KExceptionHandler. See JJ2KExceptionHandler for details.

Specified by:

getCompData in interface BlkImgDataSrc

Parameters:

blk - Its coordinates and dimensions specify the area to return. If it contains a non-null data array, then it must have the correct dimensions. If it contains a null data array a new one is created. The fields in this object are modified to return the data.

c - The index of the component from which to get the data. Only 0 is valid.

Returns:

The requested DataBlk

See Also:

getInternCompData(ucar.jpeg.jj2000.j2k.image.DataBlk, int), JJ2KExceptionHandler

isOrigSigned

public boolean isOrigSigned(int c)

Returns true if the data read was originally signed in the specified component, false if not.

Specified by:

isOrigSigned in class ImgReader

Parameters:

c - The index of the component, from 0 to N-1.

Returns:

true if the data was originally signed, false if not.

toString

public String toString()

Returns a string of information about the object, more than 1 line long. The information string includes information from the underlying RandomAccessIO (its toString() method is called in turn).

Overrides:

toString in class Object

Returns:

A string of information about the object.