[FFmpeg-devel] [PATCH 1/1] Implement gray world color correction uses log LAB colorspace
Paul Buxton
paulbuxton.mail at googlemail.com
Mon Aug 23 02:52:59 EEST 2021
Signed-off-by: Paul Buxton <paulbuxton.mail at googlemail.com>
---
doc/filters.texi | 12 ++
libavfilter/Makefile | 1 +
libavfilter/allfilters.c | 1 +
libavfilter/version.h | 2 +-
libavfilter/vf_grayworld.c | 368 +++++++++++++++++++++++++++++++++++++
5 files changed, 383 insertions(+), 1 deletion(-)
create mode 100644 libavfilter/vf_grayworld.c
diff --git a/doc/filters.texi b/doc/filters.texi
index 47ceeb18c6..0f334c3d2a 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -13046,6 +13046,18 @@ Set upper limit for video rate of output stream, Default value is @var{25}.
This guarantee that output video frame rate will not be higher than this value.
@end table
+ at section grayworld
+A color constancy filter that applies color correction based on the grayworld assumption
+
+See: @url{https://www.researchgate.net/publication/275213614_A_New_Color_Correction_Method_for_Underwater_Imaging}
+
+The algorithm uses linear light, so input
+data should be linearized beforehand (and possibly correctly tagged).
+
+ at example
+ffmpeg -i INPUT -vf zscale=transfer=linear,grayworld,zscale=transfer=bt709,format=yuv420p OUTPUT
+ at end example
+
@section greyedge
A color constancy variation filter which estimates scene illumination via grey edge algorithm
and corrects the scene colors accordingly.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 3166e70b58..1d86110d6b 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -287,6 +287,7 @@ OBJS-$(CONFIG_GBLUR_FILTER) += vf_gblur.o
OBJS-$(CONFIG_GEQ_FILTER) += vf_geq.o
OBJS-$(CONFIG_GRADFUN_FILTER) += vf_gradfun.o
OBJS-$(CONFIG_GRAPHMONITOR_FILTER) += f_graphmonitor.o
+OBJS-$(CONFIG_GRAYWORLD_FILTER) += vf_grayworld.o
OBJS-$(CONFIG_GREYEDGE_FILTER) += vf_colorconstancy.o
OBJS-$(CONFIG_GUIDED_FILTER) += vf_guided.o
OBJS-$(CONFIG_HALDCLUT_FILTER) += vf_lut3d.o framesync.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index c49c831203..73e5fe1a41 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -272,6 +272,7 @@ extern const AVFilter ff_vf_gblur;
extern const AVFilter ff_vf_geq;
extern const AVFilter ff_vf_gradfun;
extern const AVFilter ff_vf_graphmonitor;
+extern const AVFilter ff_vf_grayworld;
extern const AVFilter ff_vf_greyedge;
extern const AVFilter ff_vf_guided;
extern const AVFilter ff_vf_haldclut;
diff --git a/libavfilter/version.h b/libavfilter/version.h
index e9a76c5ac3..e3a86d9b01 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -30,7 +30,7 @@
#include "libavutil/version.h"
#define LIBAVFILTER_VERSION_MAJOR 8
-#define LIBAVFILTER_VERSION_MINOR 4
+#define LIBAVFILTER_VERSION_MINOR 5
#define LIBAVFILTER_VERSION_MICRO 100
diff --git a/libavfilter/vf_grayworld.c b/libavfilter/vf_grayworld.c
new file mode 100644
index 0000000000..c33e5c8c21
--- /dev/null
+++ b/libavfilter/vf_grayworld.c
@@ -0,0 +1,368 @@
+/*
+ * Copyright (c) 2021 Paul Buxton
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser 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
+ * Color correction filter based on
+ * https://www.researchgate.net/publication/275213614_A_New_Color_Correction_Method_for_Underwater_Imaging
+ *
+ */
+
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
+#include "libavutil/intreadwrite.h"
+
+#include "avfilter.h"
+#include "drawutils.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct ThreadData {
+ AVFrame *in, *out;
+ float l_avg;
+ float a_avg;
+ float b_avg;
+ const AVPixFmtDescriptor *desc;
+ const AVPixFmtDescriptor *odesc;
+} ThreadData;
+
+typedef struct GrayWorldContext {
+ const AVClass* class;
+ float *tmpplab;
+ int *line_count_pels;
+ float *line_sum;
+
+} GrayWorldContext;
+
+#define OFFSET(x) offsetof(GrayWorldContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_RUNTIME_PARAM
+static const AVOption grayworld_options[] = {};
+
+AVFILTER_DEFINE_CLASS(grayworld);
+
+void compute_correction(GrayWorldContext *s, ThreadData *td);
+void apply_matrix(float matrix[3][3], float input[3], float output[3]);
+void rgb2lab(float rgb[3], float lab[3]);
+void lab2rgb(float lab[3], float rgb[3]);
+
+static int query_formats(AVFilterContext *ctx)
+{
+ static const enum AVPixelFormat pix_fmts[] = {
+ AV_PIX_FMT_GBRPF32,
+ AV_PIX_FMT_GBRAPF32,
+ AV_PIX_FMT_NONE,
+ };
+ return ff_set_common_formats_from_list(ctx, pix_fmts);
+}
+
+void apply_matrix(float matrix[3][3], float input[3], float output[3])
+{
+ for (int row = 0; row < 3; ++row) {
+ output[row] = matrix[row][0] * input[0] + matrix[row][1] * input[1] + matrix[row][2] * input[2];
+ }
+}
+
+float lms2lab[3][3] = {
+ {0.5774, 0.5774, 0.5774},
+ {0.40825, 0.40825, -0.816458},
+ {0.707, -0.707, 0}
+};
+
+float lab2lms[3][3] = {
+ {0.57735, 0.40825, 0.707},
+ {0.57735, 0.40825, -0.707},
+ {0.57735, -0.8165, 0}
+};
+
+float rgb2lms[3][3] = {
+ {0.3811, 0.5783, 0.0402},
+ {0.1967, 0.7244, 0.0782},
+ {0.0241, 0.1288, 0.8444}
+};
+
+float lms2rgb[3][3] = {
+ {4.4679, -3.5873, 0.1193},
+ {-1.2186, 2.3809, -0.1624},
+ {0.0497, -0.2439, 1.2045}
+};
+
+/**
+ * Convert from Linear RGB to logspace LAB
+ *
+ * @param rgb Input array of rgb components
+ * @param lab output array of lab components
+ */
+void rgb2lab(float rgb[3], float lab[3])
+{
+ float lms[3];
+ apply_matrix(rgb2lms, rgb, lms);
+ lms[0] = logf(lms[0]);
+ lms[1] = logf(lms[1]);
+ lms[2] = logf(lms[2]);
+ apply_matrix(lms2lab, lms, lab);
+}
+
+/**
+ * Convert from Logspace LAB to Linear RGB
+ *
+ * @param lab input array of lab components
+ * @param rgb output array of rgb components
+ */
+void lab2rgb(float lab[3], float rgb[3])
+{
+ float lms[3];
+ apply_matrix(lab2lms, lab, lms);
+ lms[0] = expf(lms[0]);
+ lms[1] = expf(lms[1]);
+ lms[2] = expf(lms[2]);
+ apply_matrix(lms2rgb, lms, rgb);
+}
+
+/**
+ *
+ * Convert a frame from linear RGB to logspace LAB, and accumulate channel totals for each row
+ * Convert from RGB -> lms using equation 4 in color transfer paper.
+ *
+ * @param ctx Filter context
+ * @param arg Thread data pointer
+ * @param jobnr job number
+ * @param nb_jobs number of jobs
+ */
+static int convert_frame(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+ GrayWorldContext *s = ctx->priv;
+ ThreadData *td = arg;
+ AVFrame *in = td->in;
+ AVFrame *out = td->out;
+ AVFilterLink *outlink = ctx->outputs[0];
+ const int slice_start = (out->height * jobnr) / nb_jobs;
+ const int slice_end = (out->height * (jobnr + 1)) / nb_jobs;
+ float rgb[3];
+ float lab[3];
+
+ for (unsigned int i = slice_start; i < slice_end; i++) {
+ float *b_in_row = (float*)(in->data[1] + i * in->linesize[1]);
+ float *g_in_row = (float*)(in->data[0] + i * in->linesize[0]);
+ float *r_in_row = (float*)(in->data[2] + i * in->linesize[2]);
+ float *acur = s->tmpplab + i * outlink->w + outlink->w * outlink->h;
+ float *bcur = s->tmpplab + i * outlink->w + 2 * outlink->w * outlink->h;
+ float *lcur = s->tmpplab + i * outlink->w;
+
+ s->line_sum[i] = 0.0f;
+ s->line_sum[i + outlink->h] = 0.0f;
+ s->line_count_pels[i] = 0;
+
+ for (unsigned int j = 0; j < outlink->w; j++) {
+ rgb[0] = r_in_row[j];
+ rgb[1] = g_in_row[j];
+ rgb[2] = b_in_row[j];
+ rgb2lab(rgb, lab);
+ *(lcur++) = lab[0];
+ *(acur++) = lab[1];
+ *(bcur++) = lab[2];
+ s->line_sum[i] += lab[1];
+ s->line_sum[i + outlink->h] += lab[2];
+ s->line_count_pels[i]++;
+ }
+ }
+ return 0;
+}
+
+/**
+ *
+ * Sum the channel totals and compute the median for each channel
+ *
+ * @param s Frame context
+ * @param td thread data
+ */
+void compute_correction(GrayWorldContext *s, ThreadData *td)
+{
+ float asum = 0.0f;
+ float bsum = 0.0f;
+ float pixels = 0;
+ for (int y = 0; y < td->out->height; ++y) {
+ asum += s->line_sum[y];
+ bsum += s->line_sum[y + td->out->height];
+ pixels += s->line_count_pels[y];
+ }
+ td->a_avg = asum / pixels;
+ td->b_avg = bsum / pixels;
+}
+
+/**
+ *
+ * Subtract the mean logspace AB values from each pixel.
+ *
+ * @param ctx Filter context
+ * @param arg Thread data pointer
+ * @param jobnr job number
+ * @param nb_jobs number of jobs
+ */
+static int correct_frame(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+ GrayWorldContext *s = ctx->priv;
+ ThreadData *td = arg;
+ AVFrame *out = td->out;
+ AVFilterLink *outlink = ctx->outputs[0];
+ const int slice_start = (out->height * jobnr) / nb_jobs;
+ const int slice_end = (out->height * (jobnr + 1)) / nb_jobs;
+ float rgb[3];
+ float lab[3];
+
+ for (int i = slice_start; i < slice_end; i++) {
+ float *g_out_row = (float*)(out->data[0] + i * out->linesize[0]);
+ float *b_out_row = (float*)(out->data[1] + i * out->linesize[1]);
+ float *r_out_row = (float*)(out->data[2] + i * out->linesize[2]);
+ float *lcur = s->tmpplab + i * outlink->w;
+ float *acur = s->tmpplab + i * outlink->w + outlink->w * outlink->h;
+ float *bcur = s->tmpplab + i * outlink->w + 2 * outlink->w * outlink->h;
+
+ for (int j = 0; j < outlink->w; j++) {
+ lab[0] = *lcur++;
+ lab[1] = *acur++;
+ lab[2] = *bcur++;
+
+ // subtract the average for the color channels
+ lab[1] -= td->a_avg;
+ lab[2] -= td->b_avg;
+
+ //convert back to linear rgb
+ lab2rgb(lab, rgb);
+ r_out_row[j] = rgb[0];
+ g_out_row[j] = rgb[1];
+ b_out_row[j] = rgb[2];
+ }
+ }
+ return 0;
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+ GrayWorldContext *s = inlink->dst->priv;
+
+ s->tmpplab = av_malloc_array(inlink->h * inlink->w * 3, sizeof(float) );
+ if( !s->tmpplab){
+ return AVERROR(ENOMEM);
+ }
+ s->line_count_pels = av_malloc_array(inlink->h, sizeof(int));
+ if( !s->line_count_pels){
+ return AVERROR(ENOMEM);
+ }
+ s->line_sum = av_malloc_array(inlink->h * 2, sizeof(float));
+ if( !s->line_sum){
+ return AVERROR(ENOMEM);
+ }
+
+ return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+ GrayWorldContext *s = ctx->priv;
+
+ av_freep(&s->tmpplab);
+ av_freep(&s->line_count_pels);
+ av_freep(&s->line_sum);
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+ AVFilterContext *ctx = inlink->dst;
+ GrayWorldContext *s = ctx->priv;
+ AVFilterLink *outlink = ctx->outputs[0];
+ ThreadData td;
+ AVFrame *out;
+ const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+ const AVPixFmtDescriptor *odesc = av_pix_fmt_desc_get(outlink->format);
+
+ if (av_frame_is_writable(in)) {
+ out = in;
+ } else {
+ out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+ if (!out) {
+ av_frame_free(&in);
+ return AVERROR(ENOMEM);
+ }
+ av_frame_copy_props(out, in);
+ }
+ /* input and output transfer will be linear */
+ if (in->color_trc == AVCOL_TRC_UNSPECIFIED) {
+ av_log(s, AV_LOG_WARNING, "Untagged transfer, assuming linear light\n");
+ out->color_trc = AVCOL_TRC_LINEAR;
+ } else if (in->color_trc != AVCOL_TRC_LINEAR) {
+ av_log(s, AV_LOG_WARNING, "Grey world color correction works on linear light only\n");
+ }
+
+ td.in = in;
+ td.out = out;
+ td.desc = desc;
+ td.odesc = odesc;
+
+ ctx->internal->execute(ctx, convert_frame, &td, NULL, FFMIN(outlink->h, ff_filter_get_nb_threads(ctx)));
+ compute_correction(s, &td);
+ ctx->internal->execute(ctx, correct_frame, &td, NULL, FFMIN(outlink->h, ff_filter_get_nb_threads(ctx)));
+
+ if (desc->flags & AV_PIX_FMT_FLAG_ALPHA && desc->flags & AV_PIX_FMT_FLAG_ALPHA) {
+ av_image_copy_plane(out->data[3], out->linesize[3],
+ in->data[3], in->linesize[3],
+ out->linesize[3], outlink->h);
+ } else if (desc->flags & AV_PIX_FMT_FLAG_ALPHA) {
+ for (int y = 0; y < out->height; y++) {
+ for (int x = 0; x < out->width; x++) {
+ AV_WN32(out->data[3] + x * desc->comp[3].step + y * out->linesize[3],
+ av_float2int(1.0f));
+ }
+ }
+ }
+
+ if (in != out)
+ av_frame_free(&in);
+ return ff_filter_frame(outlink, out);
+}
+
+static const AVFilterPad grayworld_inputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO,
+ .filter_frame = filter_frame,
+ .config_props = config_input,
+ }
+};
+
+static const AVFilterPad grayworld_outputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO,
+ }
+};
+
+const AVFilter ff_vf_grayworld = {
+ .name = "grayworld",
+ .description = NULL_IF_CONFIG_SMALL("Adjust white balance using LAB gray world algorithm"),
+ .priv_size = sizeof(GrayWorldContext),
+ .priv_class = &grayworld_class,
+ .query_formats = query_formats,
+ FILTER_INPUTS(grayworld_inputs),
+ FILTER_OUTPUTS(grayworld_outputs),
+ .flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,
+ .uninit = uninit,
+};
--
2.17.1
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