C# Class CSJ2K.j2k.image.input.ImgReaderPGM

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.

Inheritance: ImgReader
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Public Properties

Property Type Description
DC_OFFSET int

Public Methods

Method Description
ImgReaderPGM ( IFileInfo file ) : System

Creates a new PGM file reader from the specified file.
ImgReaderPGM ( System fname ) : System

Creates a new PGM file reader from the specified file name.
ToString ( ) : System.String

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).
close ( ) : void

Closes the underlying RandomAccessFile from where the image data is being read. No operations are possible after a call to this method.
getCompData ( CSJ2K.j2k.image.DataBlk blk, int c ) : CSJ2K.j2k.image.DataBlk

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.
getFixedPoint ( int c ) : int

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.
getInternCompData ( CSJ2K.j2k.image.DataBlk blk, int c ) : CSJ2K.j2k.image.DataBlk

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.
getNomRangeBits ( int c ) : int

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.
isOrigSigned ( int c ) : bool

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.

Private Methods

Method Description
confirmFileType ( ) : void

Checks that the RandomAccessIO begins with 'P5'
countedByteRead ( ) : byte

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
readHeaderInt ( ) : int

Returns an int read from the header of the PGM file.
skipCommentAndWhiteSpace ( ) : void

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

Method Details

ImgReaderPGM() public method

Creates a new PGM file reader from the specified file.
If an error occurs while opening the file. /// ///
public ImgReaderPGM ( IFileInfo file ) : System
file IFileInfo The input file. /// ///
return System

ImgReaderPGM() public method

Creates a new PGM file reader from the specified file name.
If an error occurs while opening the file. /// ///
public ImgReaderPGM ( System fname ) : System
fname System The input file name. /// ///
return System

ToString() public method

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).
public ToString ( ) : System.String
return System.String

close() public method

Closes the underlying RandomAccessFile from where the image data is being read. No operations are possible after a call to this method.
If an I/O error occurs. /// ///
public close ( ) : void
return void

getCompData() public method

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.

public getCompData ( CSJ2K.j2k.image.DataBlk blk, int c ) : CSJ2K.j2k.image.DataBlk
blk CSJ2K.j2k.image.DataBlk 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 int The index of the component from which to get the data. Only 0 /// is valid. /// ///
return CSJ2K.j2k.image.DataBlk

getFixedPoint() public method

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.
public getFixedPoint ( int c ) : int
c int The index of the component. /// ///
return int

getInternCompData() public method

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.

public getInternCompData ( CSJ2K.j2k.image.DataBlk blk, int c ) : CSJ2K.j2k.image.DataBlk
blk CSJ2K.j2k.image.DataBlk Its coordinates and dimensions specify the area to /// return. Some fields in this object are modified to return the data. /// ///
c int The index of the component from which to get the data. Only 0 /// is valid. /// ///
return CSJ2K.j2k.image.DataBlk

getNomRangeBits() public method

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.

public getNomRangeBits ( int c ) : int
c int The index of the component. /// ///
return int

isOrigSigned() public method

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.
public isOrigSigned ( int c ) : bool
c int The index of the component, from 0 to N-1. /// ///
return bool

Property Details

DC_OFFSET public_oe static_oe property

DC offset value used when reading image
public static int DC_OFFSET
return int