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/*
* $RCSfile: AnWTFilterIntLift5x3.java,v $
* $Revision: 1.1 $
* $Date: 2005/02/11 05:02:29 $
* $State: Exp $
*
* Class: AnWTFilterIntLift5x3
*
* Description: An analyzing wavelet filter implementing the
* lifting 5x3 transform.
*
*
*
* COPYRIGHT:
*
* This software module was originally developed by Raphaël Grosbois and
* Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel
* Askelöf (Ericsson Radio Systems AB); and Bertrand Berthelot, David
* Bouchard, Félix Henry, Gerard Mozelle and Patrice Onno (Canon Research
* Centre France S.A) in the course of development of the JPEG2000
* standard as specified by ISO/IEC 15444 (JPEG 2000 Standard). This
* software module is an implementation of a part of the JPEG 2000
* Standard. Swiss Federal Institute of Technology-EPFL, Ericsson Radio
* Systems AB and Canon Research Centre France S.A (collectively JJ2000
* Partners) agree not to assert against ISO/IEC and users of the JPEG
* 2000 Standard (Users) any of their rights under the copyright, not
* including other intellectual property rights, for this software module
* with respect to the usage by ISO/IEC and Users of this software module
* or modifications thereof for use in hardware or software products
* claiming conformance to the JPEG 2000 Standard. Those intending to use
* this software module in hardware or software products are advised that
* their use may infringe existing patents. The original developers of
* this software module, JJ2000 Partners and ISO/IEC assume no liability
* for use of this software module or modifications thereof. No license
* or right to this software module is granted for non JPEG 2000 Standard
* conforming products. JJ2000 Partners have full right to use this
* software module for his/her own purpose, assign or donate this
* software module to any third party and to inhibit third parties from
* using this software module for non JPEG 2000 Standard conforming
* products. This copyright notice must be included in all copies or
* derivative works of this software module.
*
* Copyright (c) 1999/2000 JJ2000 Partners.
* */
package jj2000.j2k.wavelet.analysis;
import jj2000.j2k.wavelet.*;
import jj2000.j2k.image.*;
import jj2000.j2k.*;
import jj2000.j2k.codestream.writer.*;
/**
* This class inherits from the analysis wavelet filter definition for int
* data. It implements the forward wavelet transform specifically for the 5x3
* filter. The implementation is based on the lifting scheme.
*
* <P>See the AnWTFilter class for details such as normalization, how to split
* odd-length signals, etc. In particular, this method assumes that the
* low-pass coefficient is computed first.
*
* @see AnWTFilter
* @see AnWTFilterInt
* */
public class AnWTFilterIntLift5x3 extends AnWTFilterInt {
/** The low-pass synthesis filter of the 5x3 wavelet transform */
private final static float LPSynthesisFilter[] =
{ 0.5f, 1f, 0.5f };
/** The high-pass synthesis filter of the 5x3 wavelet transform */
private final static float HPSynthesisFilter[] =
{ -0.125f, -0.25f, 0.75f, -0.25f, -0.125f };
/**
* An implementation of the analyze_lpf() method that works on int data,
* for the forward 5x3 wavelet transform using the lifting scheme. See the
* general description of the analyze_lpf() method in the AnWTFilter class
* for more details.
*
* <P>The coefficients of the first lifting step are [-1/2 1 -1/2].
*
* <P>The coefficients of the second lifting step are [1/4 1 1/4].
*
* @param inSig This is the array that contains the input
* signal.
*
* @param inOff This is the index in inSig of the first sample to
* filter.
*
* @param inLen This is the number of samples in the input signal
* to filter.
*
* @param inStep This is the step, or interleave factor, of the
* input signal samples in the inSig array.
*
* @param lowSig This is the array where the low-pass output
* signal is placed.
*
* @param lowOff This is the index in lowSig of the element where
* to put the first low-pass output sample.
*
* @param lowStep This is the step, or interleave factor, of the
* low-pass output samples in the lowSig array.
*
* @param highSig This is the array where the high-pass output
* signal is placed.
*
* @param highOff This is the index in highSig of the element where
* to put the first high-pass output sample.
*
* @param highStep This is the step, or interleave factor, of the
* high-pass output samples in the highSig array.
* */
public
void analyze_lpf(int inSig[], int inOff, int inLen, int inStep,
int lowSig[], int lowOff, int lowStep,
int highSig[], int highOff, int highStep) {
int i;
int iStep = 2 * inStep; //Subsampling in inSig
int ik; //Indexing inSig
int lk; //Indexing lowSig
int hk; //Indexing highSig
/*
*Generate high frequency subband
*/
//Initialize counters
ik = inOff + inStep;
hk = highOff;
//Apply first lifting step to each "inner" sample.
for(i = 1; i < inLen-1; i += 2) {
highSig[hk] = inSig[ik] -
((inSig[ik-inStep] + inSig[ik+inStep])>>1);
ik += iStep;
hk += highStep;
}
//Handle head boundary effect if input signal has even length.
if( inLen % 2 == 0 ) {
highSig[hk] = inSig[ik] - ((2*inSig[ik-inStep])>>1);
}
/*
*Generate low frequency subband
*/
//Initialize counters
ik = inOff;
lk = lowOff;
hk = highOff;
if(inLen>1) {
lowSig[lk] = inSig[ik] + ((highSig[hk] + 1)>>1);
}
else {
lowSig[lk] = inSig[ik];
}
ik += iStep;
lk += lowStep;
hk += highStep;
//Apply lifting step to each "inner" sample.
for(i = 2; i < inLen-1; i += 2) {
lowSig[lk] = inSig[ik] +
((highSig[hk-highStep] + highSig[hk] + 2)>> 2);
ik += iStep;
lk += lowStep;
hk += highStep;
}
//Handle head boundary effect if input signal has odd length.
if(inLen % 2 == 1) {
if(inLen>2) {
lowSig[lk] = inSig[ik] + ((2*highSig[hk-highStep]+2)>>2);
}
}
}
/**
* An implementation of the analyze_hpf() method that works on int data,
* for the forward 5x3 wavelet transform using the lifting scheme. See the
* general description of the analyze_hpf() method in the AnWTFilter class
* for more details.
*
* <P>The coefficients of the first lifting step are [-1/2 1 -1/2].
*
* <P>The coefficients of the second lifting step are [1/4 1 1/4].
*
* @param inSig This is the array that contains the input
* signal.
*
* @param inOff This is the index in inSig of the first sample to
* filter.
*
* @param inLen This is the number of samples in the input signal
* to filter.
*
* @param inStep This is the step, or interleave factor, of the
* input signal samples in the inSig array.
*
* @param lowSig This is the array where the low-pass output
* signal is placed.
*
* @param lowOff This is the index in lowSig of the element where
* to put the first low-pass output sample.
*
* @param lowStep This is the step, or interleave factor, of the
* low-pass output samples in the lowSig array.
*
* @param highSig This is the array where the high-pass output
* signal is placed.
*
* @param highOff This is the index in highSig of the element where
* to put the first high-pass output sample.
*
* @param highStep This is the step, or interleave factor, of the
* high-pass output samples in the highSig array.
*
* @see AnWTFilter#analyze_hpf
* */
public
void analyze_hpf(int inSig[], int inOff, int inLen, int inStep,
int lowSig[], int lowOff, int lowStep,
int highSig[], int highOff, int highStep) {
int i;
int iStep = 2 * inStep; //Subsampling in inSig
int ik; //Indexing inSig
int lk; //Indexing lowSig
int hk; //Indexing highSig
/*
*Generate high frequency subband
*/
//Initialize counters
ik = inOff;
hk = highOff;
if ( inLen>1 ) {
// apply a symmetric extension.
highSig[hk] = inSig[ik] - inSig[ik+inStep];
}
else {
// Normalize for Nyquist gain
highSig[hk] = inSig[ik]<<1;
}
ik += iStep;
hk += highStep;
//Apply first lifting step to each "inner" sample.
if ( inLen>3 ) {
for(i = 2; i < inLen-1; i += 2) {
highSig[hk] = inSig[ik] -
((inSig[ik-inStep] + inSig[ik+inStep])>>1);
ik += iStep;
hk += highStep;
}
}
//If input signal has odd length then we perform the lifting step
// i.e. apply a symmetric extension.
if( inLen%2==1 && inLen>1 ) {
highSig[hk] = inSig[ik] - inSig[ik-inStep];
}
/*
*Generate low frequency subband
*/
//Initialize counters
ik = inOff + inStep;
lk = lowOff;
hk = highOff;
for (i=1 ; i<inLen-1 ; i+=2) {
lowSig[lk] = inSig[ik] +
((highSig[hk] + highSig[hk+highStep] + 2)>> 2);
ik += iStep;
lk += lowStep;
hk += highStep;
}
if ( inLen>1 && inLen%2==0) {
// apply a symmetric extension.
lowSig[lk] = inSig[ik]+((2*highSig[hk]+2)>>2);
}
}
/**
* Returns the negative support of the low-pass analysis
* filter. That is the number of taps of the filter in the
* negative direction.
*
* @return 2
* */
public int getAnLowNegSupport() {
return 2;
}
/**
* Returns the positive support of the low-pass analysis filter. That is
* the number of taps of the filter in the negative direction.
*
* @return The number of taps of the low-pass analysis filter in the
* positive direction
* */
public int getAnLowPosSupport() {
return 2;
}
/**
* Returns the negative support of the high-pass analysis filter. That is
* the number of taps of the filter in the negative direction.
*
* @return The number of taps of the high-pass analysis filter in
* the negative direction
* */
public int getAnHighNegSupport() {
return 1;
}
/**
* Returns the positive support of the high-pass analysis filter. That is
* the number of taps of the filter in the negative direction.
*
* @return The number of taps of the high-pass analysis filter in the
* positive direction
* */
public int getAnHighPosSupport() {
return 1;
}
/**
* Returns the negative support of the low-pass synthesis filter. That is
* the number of taps of the filter in the negative direction.
*
* <P>A MORE PRECISE DEFINITION IS NEEDED
*
* @return The number of taps of the low-pass synthesis filter in the
* negative direction
* */
public int getSynLowNegSupport() {
return 1;
}
/**
* Returns the positive support of the low-pass synthesis filter. That is
* the number of taps of the filter in the negative direction.
*
* <P>A MORE PRECISE DEFINITION IS NEEDED
*
* @return The number of taps of the low-pass synthesis filter in
* the positive direction
* */
public int getSynLowPosSupport() {
return 1;
}
/**
* Returns the negative support of the high-pass synthesis filter. That is
* the number of taps of the filter in the negative direction.
*
* <P>A MORE PRECISE DEFINITION IS NEEDED
*
* @return The number of taps of the high-pass synthesis filter in the
* negative direction
* */
public int getSynHighNegSupport() {
return 2;
}
/**
* Returns the positive support of the high-pass synthesis filter. That is
* the number of taps of the filter in the negative direction.
*
* <P>A MORE PRECISE DEFINITION IS NEEDED
*
* @return The number of taps of the high-pass synthesis filter in the
* positive direction
* */
public int getSynHighPosSupport() {
return 2;
}
/**
* Returns the time-reversed low-pass synthesis waveform of the filter,
* which is the low-pass filter. This is the time-reversed impulse
* response of the low-pass synthesis filter. It is used to calculate the
* L2-norm of the synthesis basis functions for a particular subband (also
* called energy weight).
*
* <P>The returned array may not be modified (i.e. a reference to the
* internal array may be returned by the implementation of this method).
*
* @return The time-reversed low-pass synthesis waveform of the filter.
* */
public float[] getLPSynthesisFilter() {
return LPSynthesisFilter;
}
/**
* Returns the time-reversed high-pass synthesis waveform of the filter,
* which is the high-pass filter. This is the time-reversed impulse
* response of the high-pass synthesis filter. It is used to calculate the
* L2-norm of the synthesis basis functions for a particular subband (also
* called energy weight).
*
* <P>The returned array may not be modified (i.e. a reference to the
* internal array may be returned by the implementation of this method).
*
* @return The time-reversed high-pass synthesis waveform of the filter.
* */
public float[] getHPSynthesisFilter() {
return HPSynthesisFilter;
}
/**
* Returns the implementation type of this filter, as defined in this
* class, such as WT_FILTER_INT_LIFT, WT_FILTER_FLOAT_LIFT,
* WT_FILTER_FLOAT_CONVOL.
*
* @return WT_FILTER_INT_LIFT.
* */
public int getImplType() {
return WT_FILTER_INT_LIFT;
}
/**
* Returns the reversibility of the filter. A filter is considered
* reversible if it is suitable for lossless coding.
*
* @return true since the 5x3 is reversible, provided the appropriate
* rounding is performed.
* */
public boolean isReversible() {
return true;
}
/**
* Returns true if the wavelet filter computes or uses the same "inner"
* subband coefficient as the full frame wavelet transform, and false
* otherwise. In particular, for block based transforms with reduced
* overlap, this method should return false. The term "inner" indicates
* that this applies only with respect to the coefficient that are not
* affected by image boundaries processings such as symmetric extension,
* since there is not reference method for this.
*
* <P>The result depends on the length of the allowed overlap when
* compared to the overlap required by the wavelet filter. It also depends
* on how overlap processing is implemented in the wavelet filter.
*
* @param tailOvrlp This is the number of samples in the input signal
* before the first sample to filter that can be used for overlap.
*
* @param headOvrlp This is the number of samples in the input signal
* after the last sample to filter that can be used for overlap.
*
* @param inLen This is the lenght of the input signal to filter.The
* required number of samples in the input signal after the last sample
* depends on the length of the input signal.
*
* @return true if both overlaps are greater than 2, and correct
* processing is applied in the analyze() method.
* */
public boolean isSameAsFullWT(int tailOvrlp, int headOvrlp, int inLen) {
//If the input signal has even length.
if( inLen % 2 == 0) {
if( tailOvrlp >= 2 && headOvrlp >= 1 ) return true;
else return false;
}
//Else if the input signal has odd length.
else {
if( tailOvrlp >= 2 && headOvrlp >= 2 ) return true;
else return false;
}
}
/**
* Tests if the 'obj' object is the same filter as this one. Two filters
* are the same if the same filter code should be output for both filters
* by the encodeFilterCode() method.
*
* <P>Currently the implementation of this method only tests if 'obj' is
* also of the class AnWTFilterIntLift5x3.
*
* @param The object against which to test inequality.
* */
public boolean equals(Object obj) {
// To speed up test, first test for reference equality
return obj == this ||
obj instanceof AnWTFilterIntLift5x3;
}
/**
* Returns the type of filter used according to the FilterTypes interface
* (W5x3).
*
* @see FilterTypes
*
* @return The filter type.
* */
public int getFilterType(){
return FilterTypes.W5X3;
}
/** Debugging method */
public String toString(){
return "w5x3";
}
}