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
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
|
/*
* Generate a dithering matrix for downsampling images.
*
* Copyright © 2013 Wessel Dankers <wsl@fruit.je>
*
* This file is part of mpv.
*
* mpv 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 2.1 of the License, or (at your option) any later version.
*
* mpv 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 mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <libavutil/lfg.h>
#include "misc/mp_assert.h"
#include "mpv_talloc.h"
#include "dither.h"
#define MAX_SIZEB 8
#define MAX_SIZE (1 << MAX_SIZEB)
#define MAX_SIZE2 (MAX_SIZE * MAX_SIZE)
#define WRAP_SIZE2(k, x) ((unsigned int)((unsigned int)(x) & ((k)->size2 - 1)))
#define XY(k, x, y) ((unsigned int)(((x) | ((y) << (k)->sizeb))))
struct ctx {
unsigned int sizeb, size, size2;
unsigned int gauss_radius;
unsigned int gauss_middle;
uint64_t gauss[MAX_SIZE2];
unsigned int randomat[MAX_SIZE2];
bool calcmat[MAX_SIZE2];
uint64_t gaussmat[MAX_SIZE2];
unsigned int unimat[MAX_SIZE2];
AVLFG avlfg;
};
static void makegauss(struct ctx *k, unsigned int sizeb)
{
mp_assert(sizeb >= 1 && sizeb <= MAX_SIZEB);
av_lfg_init(&k->avlfg, 123);
k->sizeb = sizeb;
k->size = 1 << k->sizeb;
k->size2 = k->size * k->size;
k->gauss_radius = k->size / 2 - 1;
k->gauss_middle = XY(k, k->gauss_radius, k->gauss_radius);
unsigned int gauss_size = k->gauss_radius * 2 + 1;
unsigned int gauss_size2 = gauss_size * gauss_size;
for (unsigned int c = 0; c < k->size2; c++)
k->gauss[c] = 0;
double sigma = -log(1.5 / (double) UINT64_MAX * gauss_size2) / k->gauss_radius;
for (unsigned int gy = 0; gy <= k->gauss_radius; gy++) {
for (unsigned int gx = 0; gx <= gy; gx++) {
int cx = (int)gx - k->gauss_radius;
int cy = (int)gy - k->gauss_radius;
int sq = cx * cx + cy * cy;
double e = exp(-sqrt(sq) * sigma);
uint64_t v = e / gauss_size2 * (double) UINT64_MAX;
k->gauss[XY(k, gx, gy)] =
k->gauss[XY(k, gy, gx)] =
k->gauss[XY(k, gx, gauss_size - 1 - gy)] =
k->gauss[XY(k, gy, gauss_size - 1 - gx)] =
k->gauss[XY(k, gauss_size - 1 - gx, gy)] =
k->gauss[XY(k, gauss_size - 1 - gy, gx)] =
k->gauss[XY(k, gauss_size - 1 - gx, gauss_size - 1 - gy)] =
k->gauss[XY(k, gauss_size - 1 - gy, gauss_size - 1 - gx)] = v;
}
}
uint64_t total = 0;
for (unsigned int c = 0; c < k->size2; c++) {
uint64_t oldtotal = total;
total += k->gauss[c];
mp_assert(total >= oldtotal);
}
}
static void setbit(struct ctx *k, unsigned int c)
{
if (k->calcmat[c])
return;
k->calcmat[c] = true;
uint64_t *m = k->gaussmat;
uint64_t *me = k->gaussmat + k->size2;
uint64_t *g = k->gauss + WRAP_SIZE2(k, k->gauss_middle + k->size2 - c);
uint64_t *ge = k->gauss + k->size2;
while (g < ge)
*m++ += *g++;
g = k->gauss;
while (m < me)
*m++ += *g++;
}
static unsigned int getmin(struct ctx *k)
{
uint64_t min = UINT64_MAX;
unsigned int resnum = 0;
unsigned int size2 = k->size2;
for (unsigned int c = 0; c < size2; c++) {
if (k->calcmat[c])
continue;
uint64_t total = k->gaussmat[c];
if (total <= min) {
if (total != min) {
min = total;
resnum = 0;
}
k->randomat[resnum++] = c;
}
}
if (resnum == 1)
return k->randomat[0];
if (resnum == size2)
return size2 / 2;
return k->randomat[av_lfg_get(&k->avlfg) % resnum];
}
static void makeuniform(struct ctx *k)
{
unsigned int size2 = k->size2;
for (unsigned int c = 0; c < size2; c++) {
unsigned int r = getmin(k);
setbit(k, r);
k->unimat[r] = c;
}
}
// out_matrix is a reactangular tsize * tsize array, where tsize = (1 << size).
void mp_make_fruit_dither_matrix(float *out_matrix, int size)
{
struct ctx *k = talloc_zero(NULL, struct ctx);
makegauss(k, size);
makeuniform(k);
float invscale = k->size2;
for(unsigned int y = 0; y < k->size; y++) {
for(unsigned int x = 0; x < k->size; x++)
out_matrix[x + y * k->size] = k->unimat[XY(k, x, y)] / invscale;
}
talloc_free(k);
}
void mp_make_ordered_dither_matrix(unsigned char *m, int size)
{
m[0] = 0;
for (int sz = 1; sz < size; sz *= 2) {
int offset[] = {sz*size, sz, sz * (size+1), 0};
for (int i = 0; i < 4; i++)
for (int y = 0; y < sz * size; y += size)
for (int x = 0; x < sz; x++)
m[x+y+offset[i]] = m[x+y] * 4 + (3-i) * 256/size/size;
}
}
|
