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/*
* $Id: filterbank.h,v 1.17 2010/02/05 23:50:22 simakov Exp $
*
* EPSILON - wavelet image compression library.
* Copyright (C) 2006,2007,2010 Alexander Simakov, <xander@entropyware.info>
*
* This file is part of EPSILON
*
* EPSILON is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* EPSILON is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with EPSILON. If not, see <http://www.gnu.org/licenses/>.
*
* http://epsilon-project.sourceforge.net
*/
/** \file
*
* \brief Filter banks
*
* This file holds defines for filter and filterbank
* data structures.
*
* \section References
*
* Gilbert Strang, Truong Nguyen "Wavelets and Filter Banks". */
#ifndef __FILTERBANK_H__
#define __FILTERBANK_H__
#ifdef __cplusplus
extern "C" {
#endif
/** \addtogroup wavelet Wavelet transform */
/*@{*/
#include <common.h>
/** Causal filter: h[i] = 0, i < 0 */
#define CAUSAL 0
/** Anticausal filter: h[i] = 0, i > 0 */
#define ANTICAUSAL 1
/** Symmetric-whole filter: h[-i] = h[i] */
#define SYMMETRIC_WHOLE 2
/** Symmetric-half filter: h[-i] = h[i - 1] */
#define SYMMETRIC_HALF 3
/** Lowpass analysis filter */
#define LOWPASS_ANALYSIS 0
/** Highpass analysis filter */
#define HIGHPASS_ANALYSIS 1
/** Lowpass synthesis filter */
#define LOWPASS_SYNTHESIS 2
/** Highpass synthesis filter */
#define HIGHPASS_SYNTHESIS 3
/** Orthogonal filterbank */
#define ORTHOGONAL 0
/** Biothogonal filterbank */
#define BIORTHOGONAL 1
/** Even subsampling phase */
#define PHASE_EVEN 0
/** Odd subsampling phase */
#define PHASE_ODD 1
/** Filter structure
*
* This structure represents a standalone filter.
*
* \note There is no need to keep all coefficients for symmetric
* filters. Only half (h[i], i >= 0) of them is kept. */
typedef struct filter_t_tag {
/** Filter length */
int length;
/** Filter causality */
int causality;
/** Filter type */
int type;
/** Filter coefficients */
coeff_t *coeffs;
} filter_t;
/** Filterbank structure
*
* Filter bank consists of two filter pairs. */
typedef struct filterbank_t_tag {
/** Short filter name (for a program) */
char *id;
/** Long filter name (for a user) */
char *name;
/** Filterbank type */
int type;
/** Lowpass analysis filter */
filter_t *lowpass_analysis;
/** Highpass analysis filter */
filter_t *highpass_analysis;
/** Lowpass synthesis filter */
filter_t *lowpass_synthesis;
/** Highpass synthesis filter */
filter_t *highpass_synthesis;
} filterbank_t;
/** External array of all available filter banks
*
* This array hold pointers to all available filter banks.
* Last element is always \c NULL. */
extern filterbank_t *filterbanks[];
/*@}*/
#ifdef __cplusplus
}
#endif
#endif /* __FILTERBANK_H__ */
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