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
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
|
/*
* Copyright (c) 2012 Jeremy Tran
* Copyright (c) 2001 Donald A. Graft
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* FFmpeg 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with FFmpeg; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/**
* @file
* Histogram equalization filter, based on the VirtualDub filter by
* Donald A. Graft <neuron2 AT home DOT com>.
* Implements global automatic contrast adjustment by means of
* histogram equalization.
*/
#include "libavutil/common.h"
#include "libavutil/internal.h"
#include "libavutil/opt.h"
#include "libavutil/pixdesc.h"
#include "avfilter.h"
#include "drawutils.h"
#include "internal.h"
#include "video.h"
// #define DEBUG
// Linear Congruential Generator, see "Numerical Recipes"
#define LCG_A 4096
#define LCG_C 150889
#define LCG_M 714025
#define LCG(x) (((x) * LCG_A + LCG_C) % LCG_M)
#define LCG_SEED 739187
enum HisteqAntibanding {
HISTEQ_ANTIBANDING_NONE = 0,
HISTEQ_ANTIBANDING_WEAK = 1,
HISTEQ_ANTIBANDING_STRONG = 2,
HISTEQ_ANTIBANDING_NB,
};
typedef struct HisteqContext {
const AVClass *class;
float strength;
float intensity;
int antibanding; ///< HisteqAntibanding
int in_histogram [256]; ///< input histogram
int out_histogram[256]; ///< output histogram
int LUT[256]; ///< lookup table derived from histogram[]
uint8_t rgba_map[4]; ///< components position
int bpp; ///< bytes per pixel
} HisteqContext;
#define OFFSET(x) offsetof(HisteqContext, x)
#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
#define CONST(name, help, val, u) { name, help, 0, AV_OPT_TYPE_CONST, {.i64=val}, INT_MIN, INT_MAX, FLAGS, .unit = u }
static const AVOption histeq_options[] = {
{ "strength", "set the strength", OFFSET(strength), AV_OPT_TYPE_FLOAT, {.dbl=0.2}, 0, 1, FLAGS },
{ "intensity", "set the intensity", OFFSET(intensity), AV_OPT_TYPE_FLOAT, {.dbl=0.21}, 0, 1, FLAGS },
{ "antibanding", "set the antibanding level", OFFSET(antibanding), AV_OPT_TYPE_INT, {.i64=HISTEQ_ANTIBANDING_NONE}, 0, HISTEQ_ANTIBANDING_NB-1, FLAGS, .unit = "antibanding" },
CONST("none", "apply no antibanding", HISTEQ_ANTIBANDING_NONE, "antibanding"),
CONST("weak", "apply weak antibanding", HISTEQ_ANTIBANDING_WEAK, "antibanding"),
CONST("strong", "apply strong antibanding", HISTEQ_ANTIBANDING_STRONG, "antibanding"),
{ NULL }
};
AVFILTER_DEFINE_CLASS(histeq);
static av_cold int init(AVFilterContext *ctx)
{
HisteqContext *histeq = ctx->priv;
av_log(ctx, AV_LOG_VERBOSE,
"strength:%0.3f intensity:%0.3f antibanding:%d\n",
histeq->strength, histeq->intensity, histeq->antibanding);
return 0;
}
static const enum AVPixelFormat pix_fmts[] = {
AV_PIX_FMT_ARGB, AV_PIX_FMT_RGBA, AV_PIX_FMT_ABGR, AV_PIX_FMT_BGRA,
AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24,
AV_PIX_FMT_NONE
};
static int config_input(AVFilterLink *inlink)
{
AVFilterContext *ctx = inlink->dst;
HisteqContext *histeq = ctx->priv;
const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(inlink->format);
histeq->bpp = av_get_bits_per_pixel(pix_desc) / 8;
ff_fill_rgba_map(histeq->rgba_map, inlink->format);
return 0;
}
#define R 0
#define G 1
#define B 2
#define A 3
#define GET_RGB_VALUES(r, g, b, src, map) do { \
r = src[x + map[R]]; \
g = src[x + map[G]]; \
b = src[x + map[B]]; \
} while (0)
static int filter_frame(AVFilterLink *inlink, AVFrame *inpic)
{
AVFilterContext *ctx = inlink->dst;
HisteqContext *histeq = ctx->priv;
AVFilterLink *outlink = ctx->outputs[0];
int strength = histeq->strength * 1000;
int intensity = histeq->intensity * 1000;
int x, y, i, luthi, lutlo, lut, luma, oluma, m;
AVFrame *outpic;
unsigned int r, g, b, jran;
uint8_t *src, *dst;
outpic = ff_get_video_buffer(outlink, outlink->w, outlink->h);
if (!outpic) {
av_frame_free(&inpic);
return AVERROR(ENOMEM);
}
av_frame_copy_props(outpic, inpic);
/* Seed random generator for antibanding. */
jran = LCG_SEED;
/* Calculate and store the luminance and calculate the global histogram
based on the luminance. */
memset(histeq->in_histogram, 0, sizeof(histeq->in_histogram));
src = inpic->data[0];
dst = outpic->data[0];
for (y = 0; y < inlink->h; y++) {
for (x = 0; x < inlink->w * histeq->bpp; x += histeq->bpp) {
GET_RGB_VALUES(r, g, b, src, histeq->rgba_map);
luma = (55 * r + 182 * g + 19 * b) >> 8;
dst[x + histeq->rgba_map[A]] = luma;
histeq->in_histogram[luma]++;
}
src += inpic->linesize[0];
dst += outpic->linesize[0];
}
#ifdef DEBUG
for (x = 0; x < 256; x++)
ff_dlog(ctx, "in[%d]: %u\n", x, histeq->in_histogram[x]);
#endif
/* Calculate the lookup table. */
histeq->LUT[0] = histeq->in_histogram[0];
/* Accumulate */
for (x = 1; x < 256; x++)
histeq->LUT[x] = histeq->LUT[x-1] + histeq->in_histogram[x];
/* Normalize */
for (x = 0; x < 256; x++)
histeq->LUT[x] = (histeq->LUT[x] * intensity) / (inlink->h * inlink->w);
/* Adjust the LUT based on the selected strength. This is an alpha
mix of the calculated LUT and a linear LUT with gain 1. */
for (x = 0; x < 256; x++)
histeq->LUT[x] = (strength * histeq->LUT[x]) / 255 +
((255 - strength) * x) / 255;
/* Output the equalized frame. */
memset(histeq->out_histogram, 0, sizeof(histeq->out_histogram));
src = inpic->data[0];
dst = outpic->data[0];
for (y = 0; y < inlink->h; y++) {
for (x = 0; x < inlink->w * histeq->bpp; x += histeq->bpp) {
luma = dst[x + histeq->rgba_map[A]];
if (luma == 0) {
for (i = 0; i < histeq->bpp; ++i)
dst[x + i] = 0;
histeq->out_histogram[0]++;
} else {
lut = histeq->LUT[luma];
if (histeq->antibanding != HISTEQ_ANTIBANDING_NONE) {
if (luma > 0) {
lutlo = histeq->antibanding == HISTEQ_ANTIBANDING_WEAK ?
(histeq->LUT[luma] + histeq->LUT[luma - 1]) / 2 :
histeq->LUT[luma - 1];
} else
lutlo = lut;
if (luma < 255) {
luthi = (histeq->antibanding == HISTEQ_ANTIBANDING_WEAK) ?
(histeq->LUT[luma] + histeq->LUT[luma + 1]) / 2 :
histeq->LUT[luma + 1];
} else
luthi = lut;
if (lutlo != luthi) {
jran = LCG(jran);
lut = lutlo + ((luthi - lutlo + 1) * jran) / LCG_M;
}
}
GET_RGB_VALUES(r, g, b, src, histeq->rgba_map);
if (((m = FFMAX3(r, g, b)) * lut) / luma > 255) {
r = (r * 255) / m;
g = (g * 255) / m;
b = (b * 255) / m;
} else {
r = (r * lut) / luma;
g = (g * lut) / luma;
b = (b * lut) / luma;
}
dst[x + histeq->rgba_map[R]] = r;
dst[x + histeq->rgba_map[G]] = g;
dst[x + histeq->rgba_map[B]] = b;
oluma = av_clip_uint8((55 * r + 182 * g + 19 * b) >> 8);
histeq->out_histogram[oluma]++;
}
}
src += inpic->linesize[0];
dst += outpic->linesize[0];
}
#ifdef DEBUG
for (x = 0; x < 256; x++)
ff_dlog(ctx, "out[%d]: %u\n", x, histeq->out_histogram[x]);
#endif
av_frame_free(&inpic);
return ff_filter_frame(outlink, outpic);
}
static const AVFilterPad histeq_inputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_VIDEO,
.config_props = config_input,
.filter_frame = filter_frame,
},
};
const AVFilter ff_vf_histeq = {
.name = "histeq",
.description = NULL_IF_CONFIG_SMALL("Apply global color histogram equalization."),
.priv_size = sizeof(HisteqContext),
.init = init,
FILTER_INPUTS(histeq_inputs),
FILTER_OUTPUTS(ff_video_default_filterpad),
FILTER_PIXFMTS_ARRAY(pix_fmts),
.priv_class = &histeq_class,
.flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
};
|
