jj2000.j2k.image.input

Class ImgReaderPGM

java.lang.Object

jj2000.j2k.image.input.ImgReader

jj2000.j2k.image.input.ImgReaderPGM

All Implemented Interfaces:

BlkImgDataSrc, ImgData

public class ImgReaderPGM
extends ImgReader

This class implements the ImgData interface for reading 8 bit unsigned data from a binary PGM file.

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

The TransferType (see ImgData) of this class is TYPE_INT.

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

See Also:

ImgData

Field Summary

Fields

Modifier and Type	Field and Description
private byte[]	buf The line buffer.
static int	DC_OFFSET DC offset value used when reading image
private RandomAccessFile	in Where to read the data from
private DataBlkInt	intBlk Temporary DataBlkInt object (needed when encoder uses floating-point filters).
private int	offset The offset of the raw pixel data in the PGM file
private int	rb The number of bits that determine the nominal dynamic range

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

h, nc, w

Constructor Summary

Constructors

Constructor and Description
ImgReaderPGM(File file) Creates a new PGM file reader from the specified file.
ImgReaderPGM(RandomAccessFile in) Creates a new PGM file reader from the specified RandomAccessFile object.
ImgReaderPGM(String fname) Creates a new PGM file reader from the specified file name.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the underlying RandomAccessFile from where the image data is being read.
private void	confirmFileType() Checks that the RandomAccessIO begins with 'P5'
private byte	countedByteRead() Returns a byte read from the RandomAccessIO.
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.
private int	readHeaderInt() Returns an int read from the header of the PGM file.
private void	skipCommentAndWhiteSpace() Skips any line in the header starting with '#' and any space, tab, line feed or carriage return.
String	toString() Returns a string of information about the object, more than 1 line long.

Methods inherited from class 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

Field Detail

DC_OFFSET

public static int DC_OFFSET

DC offset value used when reading image

in

private RandomAccessFile in

Where to read the data from

offset

private int offset

The offset of the raw pixel data in the PGM file

rb

private int rb

The number of bits that determine the nominal dynamic range

buf

private byte[] buf

The line buffer.

intBlk

private DataBlkInt intBlk

Temporary DataBlkInt object (needed when encoder uses floating-point filters). This avoid allocating new DataBlk at each time

Constructor Detail

ImgReaderPGM

public ImgReaderPGM(File file)
             throws IOException

Creates a new PGM file reader from the specified file.

Parameters:

file - The input file.

Throws:

IOException - If an error occurs while opening the file.

ImgReaderPGM

public ImgReaderPGM(String fname)
             throws IOException

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

Parameters:

fname - The input file name.

Throws:

IOException - If an error occurs while opening the file.

ImgReaderPGM

public ImgReaderPGM(RandomAccessFile in)
             throws EOFException,
                    IOException

Creates a new PGM file reader from the specified RandomAccessFile object. The file header is read to acquire the image size.

Parameters:

in - From where to read the data

Throws:

EOFException - if an EOF is read

IOException - if an error occurs when opening the file

Method Detail

close

public void close()
           throws IOException

Closes the underlying RandomAccessFile 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 rb (range bits) that was specified in the constructor, which normally is 8 for non bilevel data, and 1 for bilevel data.

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

Parameters:

c - The index of the component.

Returns:

The number of bits corresponding to the nominal range of the data. Fro floating-point data this value is not applicable and the return value is undefined.

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.

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 final 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.

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(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, n)'.

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.

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(jj2000.j2k.image.DataBlk, int), JJ2KExceptionHandler

countedByteRead

private byte countedByteRead()
                      throws IOException,
                             EOFException

Returns a byte read from the RandomAccessIO. The number of read byted are counted to keep track of the offset of the pixel data in the PGM file

Returns:

One byte read from the header of the PGM file.

Throws:

IOException - If an I/O error occurs.

EOFException - If an EOF is read

confirmFileType

private void confirmFileType()
                      throws IOException,
                             EOFException

Checks that the RandomAccessIO begins with 'P5'

Throws:

IOException - If an I/O error occurs.

EOFException - If an EOF is read

skipCommentAndWhiteSpace

private void skipCommentAndWhiteSpace()
                               throws IOException,
                                      EOFException

Skips any line in the header starting with '#' and any space, tab, line feed or carriage return.

Throws:

IOException - If an I/O error occurs.

EOFException - if an EOF is read

readHeaderInt

private int readHeaderInt()
                   throws IOException,
                          EOFException

Returns an int read from the header of the PGM file.

Returns:

One int read from the header of the PGM file.

Throws:

IOException - If an I/O error occurs.

EOFException - If an EOF is read

isOrigSigned

public boolean isOrigSigned(int c)

Returns true if the data read was originally signed in the specified component, false if not. This method returns always false since PGM data is always unsigned.

Specified by:

isOrigSigned in class ImgReader

Parameters:

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

Returns:

always false, since PGM data is always unsigned.

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.