anwtfilter.java

jpeg2000编解码

     * allows to filter columns of a 2-D signal, when it is stored in a line
     * by line order in inSig, without having to copy the data, in this case
     * the inStep argument should be the line width.</p>
     *
     * <p>The low-pass output signal is placed in the lowSig array. The lowOff
     * and lowStep arguments are analogous to the inOff and inStep ones, but
     * they apply to the lowSig array. The lowSig array must be long enough to
     * hold the low-pass output signal.</p>
     *
     * <p>The high-pass output signal is placed in the highSig array. The
     * highOff and highStep arguments are analogous to the inOff and inStep
     * ones, but they apply to the highSig array. The highSig array must be
     * long enough to hold the high-pass output signal.</p>
     *
     * @param inSig This is the array that contains the input signal. It must
     * be of the correct type (e.g., it must be int[] if getDataType() returns
     * TYPE_INT).
     *
     * @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. See above.
     *
     * @param lowSig This is the array where the low-pass output signal is
     * placed. It must be of the same type as inSig and it should be long
     * enough to contain the output signal.
     *
     * @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. See above.
     *
     * @param highSig This is the array where the high-pass output signal is
     * placed. It must be of the same type as inSig and it should be long
     * enough to contain the output signal.
     *
     * @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 above.
     *
     * @see WaveletFilter#getDataType
     * */
    public abstract 
        void analyze_hpf(Object inSig, int inOff, int inLen, int inStep, 
                     Object lowSig, int lowOff, int lowStep,
                     Object highSig, int highOff, int highStep);
                     
    /**
     * 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).</p>
     *
     * @return The time-reversed low-pass synthesis waveform of the filter.
     * */
    public abstract float[] getLPSynthesisFilter();

    /**
     * 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).</p>
     *
     * @return The time-reversed high-pass synthesis waveform of the filter.
     * */
    public abstract float[] getHPSynthesisFilter();

    /**
     * Returns the equivalent low-pass synthesis waveform of a cascade of
     * filters, given the syhthesis waveform of the previous stage. This is
     * the result of upsampling 'in' by 2, and concolving it with the low-pass
     * synthesis waveform of the filter. The length of the returned signal is
     * 2*in_l+lp_l-2, where in_l is the length of 'in' and 'lp_l' is the
     * lengthg of the low-pass synthesis filter.
     *
     * <p>The length of the low-pass synthesis filter is
     * getSynLowNegSupport()+getSynLowPosSupport().</p>
     *
     * @param in The synthesis waveform of the previous stage.
     *
     * @param out If non-null this array is used to store the resulting
     * signal. It must be long enough, or an IndexOutOfBoundsException is
     * thrown.
     *
     * @see #getSynLowNegSupport
     * @see #getSynLowPosSupport
     * */
    public float[] getLPSynWaveForm(float in[], float out[]) {
        return upsampleAndConvolve(in,getLPSynthesisFilter(),out);
    }

    /**
     * Returns the equivalent high-pass synthesis waveform of a cascade of
     * filters, given the syhthesis waveform of the previous stage. This is
     * the result of upsampling 'in' by 2, and concolving it with the
     * high-pass synthesis waveform of the filter. The length of the returned
     * signal is 2*in_l+hp_l-2, where in_l is the length of 'in' and 'hp_l' is
     * the lengthg of the high-pass synthesis filter.
     *
     * <p>The length of the high-pass synthesis filter is
     * getSynHighNegSupport()+getSynHighPosSupport().</p>
     *
     * @param in The synthesis waveform of the previous stage.
     *
     * @param out If non-null this array is used to store the resulting
     * signal. It must be long enough, or an IndexOutOfBoundsException is
     * thrown.
     *
     * @see #getSynHighNegSupport
     * @see #getSynHighPosSupport
     * */
    public float[] getHPSynWaveForm(float in[], float out[]) {
        return upsampleAndConvolve(in,getHPSynthesisFilter(),out);
    }

    /**
     * Returns the signal resulting of upsampling (by 2) the input signal 'in'
     * and then convolving it with the time-reversed signal 'wf'. The returned
     * signal is of length l_in*2+l_wf-2, where l_in is the length of 'in',
     * and l_wf is the length of 'wf'.
     *
     * <p>The 'wf' signal has to be already time-reversed, therefore only a
     * dot-product is performed (instead of a convolution). This is equivalent
     * to convolving with the non-time-reversed 'wf' signal.</p>
     *
     * @param in The signal to upsample and filter. If null it is considered
     * to be a dirac.
     *
     * @param wf The time-reversed impulse response used for filtering.
     *
     * @param out If non-null this array is used to store the resulting
     * signal, it must be of length in.length*2+wf.length-2 at least. An
     * IndexOutOfBoundsException is thrown if this is not the case.
     *
     * @return The resulting signal, of length in.length*2+wf.length-2
     * */
    private static
        float[] upsampleAndConvolve(float in[], float wf[], float out[]) {
        // NOTE: the effective length of the signal 'in' upsampled by
        // 2 is 2*in.length-1 (not 2*in.length), so the resulting signal
        // (after convolution) is of length 2*in.length-1+wf.length-1,
        // which is 2*in.length+wf.length-2

        int i,k,j;
        float tmp;
        int maxi,maxk;

        // If in null, then simulate dirac
        if (in == null) {
            in = new float[1];
            in[0] = 1.0f;
        }

        // Get output buffer if necessary
        if (out == null) {
            out = new float[in.length*2+wf.length-2];
        }
        // Convolve the signals
        for (i=0, maxi=in.length*2+wf.length-2; i<maxi; i++) {
            tmp = 0.0f;

            // Calculate limits of loop below
            k = (i-wf.length+2)/2;
            if (k<0) k = 0;
            maxk = i/2+1;
            if (maxk > in.length) maxk = in.length;

            // Calculate dot-product with upsampling of 'in' by 2.
            for (j = 2*k-i+wf.length-1; k<maxk; k++, j+=2) {
                tmp += in[k]*wf[j];
            }
            // Store result
            out[i] = tmp;
        }

        return out;
    }

    /** 
     * Returns the type of filter used according to the FilterTypes interface.
     *
     * @see FilterTypes
     *
     * @return The filter type.
     * */
    public abstract int getFilterType();

    /**
     * Returns the parameters that are used in this class and implementing
     * classes. It returns a 2D String array. Each of the 1D arrays is for a
     * different option, and they have 3 elements. The first element is the
     * option name, the second one is the synopsis, the third one is a long
     * description of what the parameter is and the fourth is its default
     * value. The synopsis or description may be 'null', in which case it is
     * assumed that there is no synopsis or description of the option,
     * respectively. Null may be returned if no options are supported.
     *
     * @return the options name, their synopsis and their explanation, or null
     * if no options are supported.
     * */
    public static String[][] getParameterInfo() {
        return pinfo;
    }

}