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vf_histeq.c
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1 /*
2  * Copyright (c) 2012 Jeremy Tran
3  * Copyright (c) 2001 Donald A. Graft
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 2 of the License, or
10  * (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License along
18  * with FFmpeg; if not, write to the Free Software Foundation, Inc.,
19  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
20  */
21 
22 /**
23  * @file
24  * Histogram equalization filter, based on the VirtualDub filter by
25  * Donald A. Graft <neuron2 AT home DOT com>.
26  * Implements global automatic contrast adjustment by means of
27  * histogram equalization.
28  */
29 
30 #include "libavutil/common.h"
31 #include "libavutil/opt.h"
32 #include "libavutil/pixdesc.h"
33 
34 #include "avfilter.h"
35 #include "drawutils.h"
36 #include "formats.h"
37 #include "internal.h"
38 #include "video.h"
39 
40 // #define DEBUG
41 
42 // Linear Congruential Generator, see "Numerical Recipes"
43 #define LCG_A 4096
44 #define LCG_C 150889
45 #define LCG_M 714025
46 #define LCG(x) (((x) * LCG_A + LCG_C) % LCG_M)
47 #define LCG_SEED 739187
48 
54 };
55 
56 typedef struct {
57  const AVClass *class;
58  float strength;
59  float intensity;
61  int in_histogram [256]; ///< input histogram
62  int out_histogram[256]; ///< output histogram
63  int LUT[256]; ///< lookup table derived from histogram[]
64  uint8_t rgba_map[4]; ///< components position
65  int bpp; ///< bytes per pixel
67 
68 #define OFFSET(x) offsetof(HisteqContext, x)
69 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
70 #define CONST(name, help, val, unit) { name, help, 0, AV_OPT_TYPE_CONST, {.i64=val}, INT_MIN, INT_MAX, FLAGS, unit }
71 
72 static const AVOption histeq_options[] = {
73  { "strength", "set the strength", OFFSET(strength), AV_OPT_TYPE_FLOAT, {.dbl=0.2}, 0, 1, FLAGS },
74  { "intensity", "set the intensity", OFFSET(intensity), AV_OPT_TYPE_FLOAT, {.dbl=0.21}, 0, 1, FLAGS },
75  { "antibanding", "set the antibanding level", OFFSET(antibanding), AV_OPT_TYPE_INT, {.i64=HISTEQ_ANTIBANDING_NONE}, 0, HISTEQ_ANTIBANDING_NB-1, FLAGS, "antibanding" },
76  CONST("none", "apply no antibanding", HISTEQ_ANTIBANDING_NONE, "antibanding"),
77  CONST("weak", "apply weak antibanding", HISTEQ_ANTIBANDING_WEAK, "antibanding"),
78  CONST("strong", "apply strong antibanding", HISTEQ_ANTIBANDING_STRONG, "antibanding"),
79  { NULL }
80 };
81 
82 AVFILTER_DEFINE_CLASS(histeq);
83 
84 static av_cold int init(AVFilterContext *ctx)
85 {
86  HisteqContext *histeq = ctx->priv;
87 
89  "strength:%0.3f intensity:%0.3f antibanding:%d\n",
90  histeq->strength, histeq->intensity, histeq->antibanding);
91 
92  return 0;
93 }
94 
96 {
97  static const enum PixelFormat pix_fmts[] = {
101  };
102 
104  return 0;
105 }
106 
107 static int config_input(AVFilterLink *inlink)
108 {
109  AVFilterContext *ctx = inlink->dst;
110  HisteqContext *histeq = ctx->priv;
111  const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(inlink->format);
112 
113  histeq->bpp = av_get_bits_per_pixel(pix_desc) / 8;
114  ff_fill_rgba_map(histeq->rgba_map, inlink->format);
115 
116  return 0;
117 }
118 
119 #define R 0
120 #define G 1
121 #define B 2
122 #define A 3
123 
124 #define GET_RGB_VALUES(r, g, b, src, map) do { \
125  r = src[x + map[R]]; \
126  g = src[x + map[G]]; \
127  b = src[x + map[B]]; \
128 } while (0)
129 
130 static int filter_frame(AVFilterLink *inlink, AVFrame *inpic)
131 {
132  AVFilterContext *ctx = inlink->dst;
133  HisteqContext *histeq = ctx->priv;
134  AVFilterLink *outlink = ctx->outputs[0];
135  int strength = histeq->strength * 1000;
136  int intensity = histeq->intensity * 1000;
137  int x, y, i, luthi, lutlo, lut, luma, oluma, m;
138  AVFrame *outpic;
139  unsigned int r, g, b, jran;
140  uint8_t *src, *dst;
141 
142  outpic = ff_get_video_buffer(outlink, outlink->w, outlink->h);
143  if (!outpic) {
144  av_frame_free(&inpic);
145  return AVERROR(ENOMEM);
146  }
147  av_frame_copy_props(outpic, inpic);
148 
149  /* Seed random generator for antibanding. */
150  jran = LCG_SEED;
151 
152  /* Calculate and store the luminance and calculate the global histogram
153  based on the luminance. */
154  memset(histeq->in_histogram, 0, sizeof(histeq->in_histogram));
155  src = inpic->data[0];
156  dst = outpic->data[0];
157  for (y = 0; y < inlink->h; y++) {
158  for (x = 0; x < inlink->w * histeq->bpp; x += histeq->bpp) {
159  GET_RGB_VALUES(r, g, b, src, histeq->rgba_map);
160  luma = (55 * r + 182 * g + 19 * b) >> 8;
161  dst[x + histeq->rgba_map[A]] = luma;
162  histeq->in_histogram[luma]++;
163  }
164  src += inpic->linesize[0];
165  dst += outpic->linesize[0];
166  }
167 
168 #ifdef DEBUG
169  for (x = 0; x < 256; x++)
170  av_dlog(ctx, "in[%d]: %u\n", x, histeq->in_histogram[x]);
171 #endif
172 
173  /* Calculate the lookup table. */
174  histeq->LUT[0] = histeq->in_histogram[0];
175  /* Accumulate */
176  for (x = 1; x < 256; x++)
177  histeq->LUT[x] = histeq->LUT[x-1] + histeq->in_histogram[x];
178 
179  /* Normalize */
180  for (x = 0; x < 256; x++)
181  histeq->LUT[x] = (histeq->LUT[x] * intensity) / (inlink->h * inlink->w);
182 
183  /* Adjust the LUT based on the selected strength. This is an alpha
184  mix of the calculated LUT and a linear LUT with gain 1. */
185  for (x = 0; x < 256; x++)
186  histeq->LUT[x] = (strength * histeq->LUT[x]) / 255 +
187  ((255 - strength) * x) / 255;
188 
189  /* Output the equalized frame. */
190  memset(histeq->out_histogram, 0, sizeof(histeq->out_histogram));
191 
192  src = inpic->data[0];
193  dst = outpic->data[0];
194  for (y = 0; y < inlink->h; y++) {
195  for (x = 0; x < inlink->w * histeq->bpp; x += histeq->bpp) {
196  luma = dst[x + histeq->rgba_map[A]];
197  if (luma == 0) {
198  for (i = 0; i < histeq->bpp; ++i)
199  dst[x + i] = 0;
200  histeq->out_histogram[0]++;
201  } else {
202  lut = histeq->LUT[luma];
203  if (histeq->antibanding != HISTEQ_ANTIBANDING_NONE) {
204  if (luma > 0) {
205  lutlo = histeq->antibanding == HISTEQ_ANTIBANDING_WEAK ?
206  (histeq->LUT[luma] + histeq->LUT[luma - 1]) / 2 :
207  histeq->LUT[luma - 1];
208  } else
209  lutlo = lut;
210 
211  if (luma < 255) {
212  luthi = (histeq->antibanding == HISTEQ_ANTIBANDING_WEAK) ?
213  (histeq->LUT[luma] + histeq->LUT[luma + 1]) / 2 :
214  histeq->LUT[luma + 1];
215  } else
216  luthi = lut;
217 
218  if (lutlo != luthi) {
219  jran = LCG(jran);
220  lut = lutlo + ((luthi - lutlo + 1) * jran) / LCG_M;
221  }
222  }
223 
224  GET_RGB_VALUES(r, g, b, src, histeq->rgba_map);
225  if (((m = FFMAX3(r, g, b)) * lut) / luma > 255) {
226  r = (r * 255) / m;
227  g = (g * 255) / m;
228  b = (b * 255) / m;
229  } else {
230  r = (r * lut) / luma;
231  g = (g * lut) / luma;
232  b = (b * lut) / luma;
233  }
234  dst[x + histeq->rgba_map[R]] = r;
235  dst[x + histeq->rgba_map[G]] = g;
236  dst[x + histeq->rgba_map[B]] = b;
237  oluma = av_clip_uint8((55 * r + 182 * g + 19 * b) >> 8);
238  histeq->out_histogram[oluma]++;
239  }
240  }
241  src += inpic->linesize[0];
242  dst += outpic->linesize[0];
243  }
244 #ifdef DEBUG
245  for (x = 0; x < 256; x++)
246  av_dlog(ctx, "out[%d]: %u\n", x, histeq->out_histogram[x]);
247 #endif
248 
249  av_frame_free(&inpic);
250  return ff_filter_frame(outlink, outpic);
251 }
252 
253 static const AVFilterPad histeq_inputs[] = {
254  {
255  .name = "default",
256  .type = AVMEDIA_TYPE_VIDEO,
257  .config_props = config_input,
258  .filter_frame = filter_frame,
259  },
260  { NULL }
261 };
262 
263 static const AVFilterPad histeq_outputs[] = {
264  {
265  .name = "default",
266  .type = AVMEDIA_TYPE_VIDEO,
267  },
268  { NULL }
269 };
270 
272  .name = "histeq",
273  .description = NULL_IF_CONFIG_SMALL("Apply global color histogram equalization."),
274  .priv_size = sizeof(HisteqContext),
275  .init = init,
277  .inputs = histeq_inputs,
278  .outputs = histeq_outputs,
279  .priv_class = &histeq_class,
281 };