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/*
* $RCSfile: SynWTFilterIntLift5x3.java,v $
* $Revision: 1.1 $
* $Date: 2005/02/11 05:02:34 $
* $State: Exp $
*
* Class: SynWTFilterIntLift5x3
*
* Description: A synthetizing 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.synthesis;
import jj2000.j2k.wavelet.*;
import jj2000.j2k.image.*;
import jj2000.j2k.*;
/**
* This class inherits from the synthesis wavelet filter definition for int
* data. It implements the inverse wavelet transform specifically for the 5x3
* filter. The implementation is based on the lifting scheme.
*
* <P>See the SynWTFilter 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 SynWTFilter
* @see SynWTFilterInt
* */
public class SynWTFilterIntLift5x3 extends SynWTFilterInt {
/**
* An implementation of the synthetize_lpf() method that works on int
* data, for the inverse 5x3 wavelet transform using the lifting
* scheme. See the general description of the synthetize_lpf() method in
* the SynWTFilter class for more details.
*
* <P>The coefficients of the first lifting step are [-1/4 1 -1/4].
*
* <P>The coefficients of the second lifting step are [1/2 1 1/2].
*
* @param lowSig This is the array that contains the low-pass
* input signal.
*
* @param lowOff This is the index in lowSig of the first sample to
* filter.
*
* @param lowLen This is the number of samples in the low-pass
* input signal to filter.
*
* @param lowStep This is the step, or interleave factor, of the
* low-pass input signal samples in the lowSig array.
*
* @param highSig This is the array that contains the high-pass
* input signal.
*
* @param highOff This is the index in highSig of the first sample to
* filter.
*
* @param highLen This is the number of samples in the high-pass
* input signal to filter.
*
* @param highStep This is the step, or interleave factor, of the
* high-pass input signal samples in the highSig array.
*
* @param outSig This is the array where the output signal is
* placed. It should be long enough to contain the output signal.
*
* @param outOff This is the index in outSig of the element where
* to put the first output sample.
*
* @param outStep This is the step, or interleave factor, of the
* output samples in the outSig array.
*
* @see SynWTFilter#synthetize_lpf
* */
public
void synthetize_lpf(int[] lowSig, int lowOff, int lowLen, int lowStep,
int[] highSig, int highOff, int highLen, int highStep,
int[] outSig, int outOff, int outStep) {
int i;
int outLen = lowLen + highLen; //Length of the output signal
int iStep = 2*outStep; //Upsampling in outSig
int ik; //Indexing outSig
int lk; //Indexing lowSig
int hk; //Indexing highSig
/*
*Generate even samples (inverse low-pass filter)
*/
//Initialize counters
lk = lowOff;
hk = highOff;
ik = outOff;
//Handle tail boundary effect. Use symmetric extension.
if(outLen>1) {
outSig[ik] = lowSig[lk] - ((highSig[hk]+1)>>1);
}
else {
outSig[ik] = lowSig[lk];
}
lk += lowStep;
hk += highStep;
ik += iStep;
//Apply lifting step to each "inner" sample.
for(i = 2; i < outLen-1; i += 2) {
outSig[ik] = lowSig[lk] -
((highSig[hk-highStep] + highSig[hk] + 2)>>2);
lk += lowStep;
hk += highStep;
ik += iStep;
}
//Handle head boundary effect if input signal has odd length.
if((outLen % 2 == 1)&&(outLen>2)) {
outSig[ik] = lowSig[lk] - ((2*highSig[hk-highStep]+2)>>2);
}
/*
*Generate odd samples (inverse high pass-filter)
*/
//Initialize counters
hk = highOff;
ik = outOff + outStep;
//Apply first lifting step to each "inner" sample.
for(i = 1; i < outLen-1; i += 2) {
// Since signs are inversed (add instead of substract)
// the +1 rounding dissapears.
outSig[ik] = highSig[hk] +
((outSig[ik-outStep] + outSig[ik+outStep]) >> 1);
hk += highStep;
ik += iStep;
}
//Handle head boundary effect if input signal has even length.
if( outLen%2==0 && outLen>1) {
outSig[ik] = highSig[hk] + outSig[ik-outStep];
}
}
/**
* An implementation of the synthetize_hpf() method that works on int
* data, for the inverse 5x3 wavelet transform using thelifting
* scheme. See the general description of the synthetize_hpf() method in
* the SynWTFilter class for more details.
*
* <P>The coefficients of the first lifting step are [-1/4 1 -1/4].
*
* <P>The coefficients of the second lifting step are [1/2 1 1/2].
*
* @param lowSig This is the array that contains the low-pass
* input signal.
*
* @param lowOff This is the index in lowSig of the first sample to
* filter.
*
* @param lowLen This is the number of samples in the low-pass
* input signal to filter.
*
* @param lowStep This is the step, or interleave factor, of the
* low-pass input signal samples in the lowSig array.
*
* @param highSig This is the array that contains the high-pass
* input signal.
*
* @param highOff This is the index in highSig of the first sample to
* filter.
*
* @param highLen This is the number of samples in the high-pass
* input signal to filter.
*
* @param highStep This is the step, or interleave factor, of the
* high-pass input signal samples in the highSig array.
*
* @param outSig This is the array where the output signal is
* placed. It should be long enough to contain the output signal.
*
* @param outOff This is the index in outSig of the element where
* to put the first output sample.
*
* @param outStep This is the step, or interleave factor, of the
* output samples in the outSig array.
*
* @see SynWTFilter#synthetize_hpf
* */
public
void synthetize_hpf(int[] lowSig, int lowOff, int lowLen, int lowStep,
int[] highSig, int highOff, int highLen, int highStep,
int[] outSig, int outOff, int outStep) {
int i;
int outLen = lowLen + highLen; //Length of the output signal
int iStep = 2*outStep; //Upsampling in outSig
int ik; //Indexing outSig
int lk; //Indexing lowSig
int hk; //Indexing highSig
/*
*Generate even samples (inverse low-pass filter)
*/
//Initialize counters
lk = lowOff;
hk = highOff;
ik = outOff + outStep;
//Apply lifting step to each "inner" sample.
for(i = 1; i<outLen-1; i += 2) {
outSig[ik] = lowSig[lk] -
((highSig[hk] + highSig[hk+highStep] + 2)>>2);
lk += lowStep;
hk += highStep;
ik += iStep;
}
if ( (outLen>1) && (outLen%2==0) ) {
// symmetric extension.
outSig[ik] = lowSig[lk] - ((2*highSig[hk]+2)>>2);
}
/*
*Generate odd samples (inverse high pass-filter)
*/
//Initialize counters
hk = highOff;
ik = outOff;
if ( outLen>1 ) {
outSig[ik] = highSig[hk] + outSig[ik+outStep];
}
else {
// Normalize for Nyquist gain
outSig[ik] = highSig[hk]>>1;
}
hk += highStep;
ik += iStep;
//Apply first lifting step to each "inner" sample.
for(i = 2; i < outLen-1; i += 2) {
// Since signs are inversed (add instead of substract)
// the +1 rounding dissapears.
outSig[ik] = highSig[hk] +
((outSig[ik-outStep] + outSig[ik+outStep]) >> 1);
hk += highStep;
ik += iStep;
}
//Handle head boundary effect if input signal has odd length.
if(outLen%2==1 && outLen>1) {
outSig[ik] = highSig[hk] + outSig[ik-outStep];
}
}
/**
* 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 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;
}
}
/**
* Returns a string of information about the synthesis wavelet filter
*
* @return wavelet filter type.
* */
public String toString(){
return "w5x3 (lifting)";
}
}