/*
 * $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.FilterTypes;

/**
 * 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";
    }
}