avfilter: add exposure video filter

Changelog

@@ -70,6 +70,7 @@ version <next>:
 - colorize filter
 - CRI parser
 - aexciter audio filter
+- exposure video filter
 
 
 version 4.3:

doc/filters.texi

@@ -11375,6 +11375,25 @@ Six-point interpolation.
 @subsection Commands
 This filter supports same @ref{commands} as options.
 
+@section exposure
+Adjust exposure of the video stream.
+
+The filter accepts the following options:
+
+@table @option
+@item exposure
+Set the exposure correction in EV. Allowed range is from -3.0 to 3.0 EV
+Default value is 0 EV.
+
+@item black
+Set the black level correction. Allowed range is from -1.0 to 1.0.
+Default value is 0.
+@end table
+
+@subsection Commands
+
+This filter supports same @ref{commands} as options.
+
 @section extractplanes
 
 Extract color channel components from input video stream into

libavfilter/Makefile

@@ -259,6 +259,7 @@ OBJS-$(CONFIG_EROSION_FILTER)                += vf_neighbor.o
 OBJS-$(CONFIG_EROSION_OPENCL_FILTER)         += vf_neighbor_opencl.o opencl.o \
                                                 opencl/neighbor.o
 OBJS-$(CONFIG_ESTDIF_FILTER)                 += vf_estdif.o
+OBJS-$(CONFIG_EXPOSURE_FILTER)               += vf_exposure.o
 OBJS-$(CONFIG_EXTRACTPLANES_FILTER)          += vf_extractplanes.o
 OBJS-$(CONFIG_FADE_FILTER)                   += vf_fade.o
 OBJS-$(CONFIG_FFTDNOIZ_FILTER)               += vf_fftdnoiz.o

libavfilter/allfilters.c

@@ -244,6 +244,7 @@ extern AVFilter ff_vf_eq;
 extern AVFilter ff_vf_erosion;
 extern AVFilter ff_vf_erosion_opencl;
 extern AVFilter ff_vf_estdif;
+extern AVFilter ff_vf_exposure;
 extern AVFilter ff_vf_extractplanes;
 extern AVFilter ff_vf_fade;
 extern AVFilter ff_vf_fftdnoiz;

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR 104
+#define LIBAVFILTER_VERSION_MINOR 105
 #define LIBAVFILTER_VERSION_MICRO 100
 
 

libavfilter/vf_exposure.c

@@ -0,0 +1,144 @@
+/*
+ * Copyright (c) 2021 Paul B Mahol
+ *
+ * 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
+ */
+
+#include <float.h>
+
+#include "libavutil/opt.h"
+#include "libavutil/imgutils.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct ExposureContext {
+    const AVClass *class;
+
+    float exposure;
+    float black;
+
+    float scale;
+    int (*do_slice)(AVFilterContext *s, void *arg,
+                    int jobnr, int nb_jobs);
+} ExposureContext;
+
+static int exposure_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
+{
+    ExposureContext *s = ctx->priv;
+    AVFrame *frame = arg;
+    const int width = frame->width;
+    const int height = frame->height;
+    const int slice_start = (height * jobnr) / nb_jobs;
+    const int slice_end = (height * (jobnr + 1)) / nb_jobs;
+    const float black = s->black;
+    const float scale = s->scale;
+
+    for (int p = 0; p < 3; p++) {
+        const int linesize = frame->linesize[p] / 4;
+        float *ptr = (float *)frame->data[p] + slice_start * linesize;
+        for (int y = slice_start; y < slice_end; y++) {
+            for (int x = 0; x < width; x++)
+                ptr[x] = (ptr[x] - black) * scale;
+
+            ptr += linesize;
+        }
+    }
+
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
+{
+    AVFilterContext *ctx = inlink->dst;
+    ExposureContext *s = ctx->priv;
+
+    s->scale = 1.f / (exp2f(-s->exposure) - s->black);
+    ctx->internal->execute(ctx, s->do_slice, frame, NULL,
+                           FFMIN(frame->height, ff_filter_get_nb_threads(ctx)));
+
+    return ff_filter_frame(ctx->outputs[0], frame);
+}
+
+static av_cold int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pixel_fmts[] = {
+        AV_PIX_FMT_GBRPF32, AV_PIX_FMT_GBRAPF32,
+        AV_PIX_FMT_NONE
+    };
+
+    AVFilterFormats *formats = NULL;
+
+    formats = ff_make_format_list(pixel_fmts);
+    if (!formats)
+        return AVERROR(ENOMEM);
+
+    return ff_set_common_formats(ctx, formats);
+}
+
+static av_cold int config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    ExposureContext *s = ctx->priv;
+
+    s->do_slice = exposure_slice;
+
+    return 0;
+}
+
+static const AVFilterPad exposure_inputs[] = {
+    {
+        .name           = "default",
+        .type           = AVMEDIA_TYPE_VIDEO,
+        .needs_writable = 1,
+        .filter_frame   = filter_frame,
+        .config_props   = config_input,
+    },
+    { NULL }
+};
+
+static const AVFilterPad exposure_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+#define OFFSET(x) offsetof(ExposureContext, x)
+#define VF AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
+
+static const AVOption exposure_options[] = {
+    { "exposure", "set the exposure correction",    OFFSET(exposure), AV_OPT_TYPE_FLOAT, {.dbl=0}, -3, 3, VF },
+    { "black",    "set the black level correction", OFFSET(black),    AV_OPT_TYPE_FLOAT, {.dbl=0}, -1, 1, VF },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(exposure);
+
+AVFilter ff_vf_exposure = {
+    .name          = "exposure",
+    .description   = NULL_IF_CONFIG_SMALL("Adjust exposure of the video stream."),
+    .priv_size     = sizeof(ExposureContext),
+    .priv_class    = &exposure_class,
+    .query_formats = query_formats,
+    .inputs        = exposure_inputs,
+    .outputs       = exposure_outputs,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,
+    .process_command = ff_filter_process_command,
+};