1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
|
/*
* $Id: dc_level.h,v 1.13 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 DC level shift
*
* In order to further improve codec perfomance, input signal must be
* centered around zero before applying wavelet transform. One can
* accomplish this by subtracting mean value from each image sample.
* This preprocessing step results in wavelet coefficient magnitude
* decrease, which in turn, reduces number of bits required for
* image encoding. After decoding, one have to perform the inverse
* operation, i.e. add stored mean value to each reconstructed image sample. */
#ifndef __DC_LEVEL_H__
#define __DC_LEVEL_H__
#ifdef __cplusplus
extern "C" {
#endif
/** \addtogroup dc_level DC level shift */
/*@{*/
#include <common.h>
/** DC level shift
*
* This function subtracts mean value from each image sample.
*
* \param channel Image channel
* \param width Image width
* \param height Image height
*
* \return Mean value */
coeff_t dc_level_shift(coeff_t **channel, int width, int height);
/** DC level unshift
*
* This function adds stored mean value to each
* reconstructed image sample.
*
* \param channel Image channel
* \param average Average (mean) value
* \param width Image width
* \param height Image height
*
* \return \c VOID */
void dc_level_unshift(coeff_t **channel, coeff_t average, int width, int height);
/*@}*/
#ifdef __cplusplus
}
#endif
#endif /* __DC_LEVEL_H__ */
|
