jj2000.j2k.image.input

Class ImgReaderPPM

java.lang.Object

jj2000.j2k.image.input.ImgReader

jj2000.j2k.image.input.ImgReaderPPM

All Implemented Interfaces:

BlkImgDataSrc, ImgData

public class ImgReaderPPM
extends ImgReader

This class implements the ImgData interface for reading 8 bits unsigned data from a binary PPM file

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

The transfer type (see ImgData) of this class is TYPE_INT.

This class is buffered: the 3 input components(R,G,B) are read when the first one (R) is asked. The 2 others are stored until they are needed.

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

See Also:

ImgData

Field Summary

Fields

Modifier and Type	Field and Description
static int	DC_OFFSET DC offset value used when reading image

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

h, nc, w

Constructor Summary

Constructors

Constructor and Description
ImgReaderPPM(File file) Creates a new PPM file reader from the specified file.
ImgReaderPPM(String fname) Creates a new PPM file reader from the specified file name.

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Closes the underlying file 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 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

Constructor Detail

ImgReaderPPM

public ImgReaderPPM(File file)
             throws IOException

Creates a new PPM file reader from the specified file.

Parameters:

file - The input file.

IOException - If an error occurs while opening the file.

Throws:

IOException

ImgReaderPPM

public ImgReaderPPM(String fname)
             throws IOException

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

Parameters:

fname - The input file name.

IOException - If an error occurs while opening the file.

Throws:

IOException

Method Detail

close

public void close()
           throws IOException

Closes the underlying file 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 avergae of 0.

Parameters:

c - The index of the component.

Returns:

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

This method implements buffering for the 3 components: When the first one is asked, all the 3 components are read and stored until they are needed.

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, 1 and 3 are valid.

Returns:

The requested DataBlk

See Also:

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

getCompData

public final 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).

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 0,1 and 2 are valid.

Returns:

The requested DataBlk

See Also:

getInternCompData(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. This method always returns false since PPM 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 PPM 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 RandomAccessFile (its toString() method is called in turn).

Overrides:

toString in class Object

Returns:

A string of information about the object.