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lavfi: add histeq filter

This is a port of virtual dub's histogram equalization filter by Donald
A. Graft. Based on the work by Jérémy Tran <tran.jeremy.av@gmail.com>,
done for SOCIS 2012.
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1 parent 172505b commit 014056635944b7b22cd25aef44f0cdc4c237e9b6 @saste saste committed Oct 20, 2012
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@@ -56,6 +56,7 @@ version <next>:
- data: URI scheme
- support building on the Plan 9 operating system
- kerndeint filter ported from MPlayer
+- histeq filter ported from VirtualDub
version 1.0:
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@@ -31,6 +31,7 @@ Specifically, the GPL parts of FFmpeg are
- vf_decimate.c
- vf_delogo.c
- vf_geq.c
+ - vf_histeq.c
- vf_hqdn3d.c
- vf_hue.c
- vf_kerndeint.c
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@@ -1985,6 +1985,7 @@ frei0r_filter_extralibs='$ldl'
frei0r_src_filter_deps="frei0r dlopen"
frei0r_src_filter_extralibs='$ldl'
geq_filter_deps="gpl"
+histeq_filter_deps="gpl"
hqdn3d_filter_deps="gpl"
hue_filter_deps="gpl"
kerndeint_filter_deps="gpl"
View
@@ -2664,6 +2664,44 @@ For example to horizontally flip the input video with @command{ffmpeg}:
ffmpeg -i in.avi -vf "hflip" out.avi
@end example
+@section histeq
+This filter applies a global color histogram equalization on a
+per-frame basis.
+
+It can be used to correct video that has a compressed range of pixel
+intensities. The filter redistributes the pixel intensities to
+equalize their distribution across the intensity range. It may be
+viewed as an "automatically adjusting contrast filter". This filter is
+useful only for correcting degraded or poorly captured source
+video.
+
+The filter accepts parameters as a list of @var{key}=@var{value}
+pairs, separated by ":". If the key of the first options is omitted,
+the arguments are interpreted according to syntax
+@var{strength}:@var{intensity}:@var{antibanding}.
+
+This filter accepts the following named options:
+
+@table @option
+@item strength
+Determine the amount of equalization to be applied. As the strength
+is reduced, the distribution of pixel intensities more-and-more
+approaches that of the input frame. The value must be a float number
+in the range [0,1] and defaults to 0.200.
+
+@item intensity
+Set the maximum intensity that can generated and scale the output
+values appropriately. The strength should be set as desired and then
+the intensity can be limited if needed to avoid washing-out. The value
+must be a float number in the range [0,1] and defaults to 0.210.
+
+@item antibanding
+Set the antibanding level. If enabled the filter will randomly vary
+the luminance of output pixels by a small amount to avoid banding of
+the histogram. Possible values are @code{none}, @code{weak} or
+@code{strong}. It defaults to @code{none}.
+@end table
+
@section hqdn3d
High precision/quality 3d denoise filter. This filter aims to reduce
@@ -111,6 +111,7 @@ OBJS-$(CONFIG_FREI0R_FILTER) += vf_frei0r.o
OBJS-$(CONFIG_GEQ_FILTER) += vf_geq.o
OBJS-$(CONFIG_GRADFUN_FILTER) += vf_gradfun.o
OBJS-$(CONFIG_HFLIP_FILTER) += vf_hflip.o
+OBJS-$(CONFIG_HISTEQ_FILTER) += vf_histeq.o
OBJS-$(CONFIG_HQDN3D_FILTER) += vf_hqdn3d.o
OBJS-$(CONFIG_HUE_FILTER) += vf_hue.o
OBJS-$(CONFIG_IDET_FILTER) += vf_idet.o
@@ -105,6 +105,7 @@ void avfilter_register_all(void)
REGISTER_FILTER(GEQ, geq, vf);
REGISTER_FILTER(GRADFUN, gradfun, vf);
REGISTER_FILTER(HFLIP, hflip, vf);
+ REGISTER_FILTER(HISTEQ, histeq, vf);
REGISTER_FILTER(HQDN3D, hqdn3d, vf);
REGISTER_FILTER(HUE, hue, vf);
REGISTER_FILTER(IDET, idet, vf);
@@ -29,7 +29,7 @@
#include "libavutil/avutil.h"
#define LIBAVFILTER_VERSION_MAJOR 3
-#define LIBAVFILTER_VERSION_MINOR 31
+#define LIBAVFILTER_VERSION_MINOR 32
#define LIBAVFILTER_VERSION_MICRO 100
#define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
@@ -0,0 +1,298 @@
+/*
+ * 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;
+ char* antibanding_str;
+ 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, const char *args)
+{
+ HisteqContext *histeq = ctx->priv;
+ const char *shorthand[] = { "strength", "intensity", "antibanding", NULL };
+ int ret;
+
+ histeq->class = &histeq_class;
+ av_opt_set_defaults(histeq);
+
+ if ((ret = av_opt_set_from_string(histeq, args, shorthand, "=", ":")) < 0)
+ return ret;
+
+ av_log(ctx, AV_LOG_VERBOSE,
+ "strength:%0.3f intensity:%0.3f antibanding:%d\n",
+ histeq->strength, histeq->intensity, histeq->antibanding);
+
+ return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+ HisteqContext *histeq = ctx->priv;
+ av_opt_free(histeq);
+}
+
+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, AVFilterBufferRef *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;
+ AVFilterBufferRef *outpic;
+ unsigned int r, g, b, jran;
+ uint8_t *src, *dst;
+
+ outpic = ff_get_video_buffer(outlink, AV_PERM_WRITE|AV_PERM_ALIGN, outlink->w, outlink->h);
+ if (!outpic) {
+ avfilter_unref_bufferp(&inpic);
+ return AVERROR(ENOMEM);
+ }
+ avfilter_copy_buffer_ref_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 = (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
+
+ avfilter_unref_bufferp(&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,
+ .min_perms = AV_PERM_READ,
+ },
+ { 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,
+ .uninit = uninit,
+ .query_formats = query_formats,
+
+ .inputs = histeq_inputs,
+ .outputs = histeq_outputs,
+ .priv_class = &histeq_class,
+};
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