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
80
81
82
83
84
85
86
|
/** \file gamma.c
*
* \author Copyright 2001 Lutz Mueller <lutz@users.sf.net>
*
* \par License
* This library 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 2 of the License, or (at your option) any later version.
*
* \par
* This library 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.
*
* \par
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301 USA
*/
#include "config.h"
#include "gamma.h"
#include <math.h>
#include <gphoto2/gphoto2-result.h>
static int
gp_gamma_correct_triple (unsigned char *table_red,
unsigned char *table_green,
unsigned char *table_blue,
unsigned char *data, unsigned int size)
{
unsigned int x;
for (x = 0; x < (size * 3); x += 3) {
data[x + 0] = table_red [data[x + 0]];
data[x + 1] = table_green[data[x + 1]];
data[x + 2] = table_blue [data[x + 2]];
}
return (GP_OK);
}
/**
* \brief Gamma correction
*
* Corrects size pixels within the table with a given Gamma
* correction table.
*
* \param table the gamma correction table as generated by gp_gamma_fill_table()
* \param data the data do process, both input and output
* \param size in number of pixels (RGB byte pairs)
*
* \returns a gphoto error code
*/
int
gp_gamma_correct_single (unsigned char *table, unsigned char *data,
unsigned int size)
{
return (gp_gamma_correct_triple (table, table, table, data, size));
}
/**
* \brief Initialize a Gamma conversion table
*
* Initializes the gamma conversion table for later use by gp_gamma_correct_single().
* Requires a 256 byte array as table.
* \param table a 256 byte array of unsigned char
* \param g gamma correction value
*
* \returns a gphoto error code
*/
int
gp_gamma_fill_table (unsigned char *table, double g)
{
unsigned int x;
for (x = 0; x < 256; x++)
table[x] = 255 * pow ((double) x/255., g);
return (GP_OK);
}
|
