/*
* 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/opt.h"
#include "libavutil/pixdesc.h"
#include "avfilter.h"
#include "drawutils.h"
#include "formats.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 {
const AVClass *class;
float strength;
float intensity;
enum HisteqAntibanding antibanding;
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, unit) { name, help, 0, AV_OPT_TYPE_CONST, {.i64=val}, INT_MIN, INT_MAX, FLAGS, unit }
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, "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 int query_formats(AVFilterContext *ctx)
{
static const enum PixelFormat 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
};
ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
return 0;
}
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++)
av_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++)
av_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,
},
{ NULL }
};
static const AVFilterPad histeq_outputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_VIDEO,
},
{ NULL }
};
AVFilter avfilter_vf_histeq = {
.name = "histeq",
.description = NULL_IF_CONFIG_SMALL("Apply global color histogram equalization."),
.priv_size = sizeof(HisteqContext),
.init = init,
.query_formats = query_formats,
.inputs = histeq_inputs,
.outputs = histeq_outputs,
.priv_class = &histeq_class,
.flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
};