lavfi: add curves filter.

Changelog

@@ -2,6 +2,10 @@ Entries are sorted chronologically from oldest to youngest within each release,
 releases are sorted from youngest to oldest.
 
 version <next>:
+- curves filter
+
+
+version 1.2:
 
 - VDPAU hardware acceleration through normal hwaccel
 - SRTP support

doc/filters.texi

@@ -2217,6 +2217,73 @@ indicates never reset and return the largest area encountered during
 playback.
 @end table
 
+@section curves
+
+Apply color adjustments using curves.
+
+This filter is similar to the Adobe Photoshop and GIMP curves tools. Each
+component (red, green and blue) has its values defined by @var{N} key points
+tied from each other using a smooth curve. The x-axis represents the pixel
+values from the input frame, and the y-axis the new pixel values to be set for
+the output frame.
+
+By default, a component curve is defined by the two points @var{(0;0)} and
+@var{(1;1)}. This creates a straight line where each original pixel value is
+"adjusted" to its own value, which means no change to the image.
+
+The filter allows you to redefine these two points and add some more. A new
+curve (using a natural cubic spline interpolation) will be define to pass
+smoothly through all these new coordinates. The new defined points needs to be
+strictly increasing over the x-axis, and their @var{x} and @var{y} values must
+be in the @var{[0;1]} interval.  If the computed curves happened to go outside
+the vector spaces, the values will be clipped accordingly.
+
+If there is no key point defined in @code{x=0}, the filter will automatically
+insert a @var{(0;0)} point. In the same way, if there is no key point defined
+in @code{x=1}, the filter will automatically insert a @var{(1;1)} point.
+
+The filter accepts parameters as a list of @var{key}=@var{value} pairs,
+separated by ":".
+
+A description of the accepted parameters follows.
+
+@table @option
+@item red, r
+Set the key points for the red component.
+@item green, g
+Set the key points for the green component.
+@item blue, b
+Set the key points for the blue component.
+@end table
+
+To avoid some filtergraph syntax conflicts, each key points list need to be
+defined using the following syntax: @code{x0/y0 x1/y1 x2/y2 ...}.
+
+@subsection Examples
+
+@itemize
+@item
+Increase slightly the middle level of blue:
+@example
+curves=blue='0.5/0.58'
+@end example
+
+@item
+Vintage effect:
+@example
+curves=r='0/0.11 .42/.51 1/0.95':g='0.50/0.48':b='0/0.22 .49/.44 1/0.8'
+@end example
+Here we obtain the following coordinates for each components:
+@table @var
+@item red
+@code{(0;0.11) (0.42;0.51) (1;0.95)}
+@item green
+@code{(0;0) (0.50;0.48) (1;1)}
+@item blue
+@code{(0;0.22) (0.49;0.44) (1;0.80)}
+@end table
+@end itemize
+
 @section decimate
 
 Drop frames that do not differ greatly from the previous frame in

libavfilter/Makefile

@@ -104,6 +104,7 @@ OBJS-$(CONFIG_COLORMATRIX_FILTER)            += vf_colormatrix.o
 OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o
 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
 OBJS-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o
+OBJS-$(CONFIG_CURVES_FILTER)                 += vf_curves.o
 OBJS-$(CONFIG_DECIMATE_FILTER)               += vf_decimate.o
 OBJS-$(CONFIG_DELOGO_FILTER)                 += vf_delogo.o
 OBJS-$(CONFIG_DESHAKE_FILTER)                += vf_deshake.o

libavfilter/allfilters.c

@@ -100,6 +100,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(COPY,           copy,           vf);
     REGISTER_FILTER(CROP,           crop,           vf);
     REGISTER_FILTER(CROPDETECT,     cropdetect,     vf);
+    REGISTER_FILTER(CURVES,         curves,         vf);
     REGISTER_FILTER(DECIMATE,       decimate,       vf);
     REGISTER_FILTER(DELOGO,         delogo,         vf);
     REGISTER_FILTER(DESHAKE,        deshake,        vf);

libavfilter/version.h

@@ -29,7 +29,7 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  3
-#define LIBAVFILTER_VERSION_MINOR  43
+#define LIBAVFILTER_VERSION_MINOR  44
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_curves.c

@@ -0,0 +1,363 @@
+/*
+ * Copyright (c) 2013 Clément Bœsch
+ *
+ * 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 "libavutil/opt.h"
+#include "libavutil/eval.h"
+#include "libavutil/avassert.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+struct keypoint {
+    double x, y;
+    struct keypoint *next;
+};
+
+#define NB_COMP 3
+
+typedef struct {
+    const AVClass *class;
+    char *comp_points_str[NB_COMP];
+    uint8_t graph[NB_COMP][256];
+} CurvesContext;
+
+#define OFFSET(x) offsetof(CurvesContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption curves_options[] = {
+    { "red",   "set red points coordinates",   OFFSET(comp_points_str[0]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "r",     "set red points coordinates",   OFFSET(comp_points_str[0]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "green", "set green points coordinates", OFFSET(comp_points_str[1]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "g",     "set green points coordinates", OFFSET(comp_points_str[1]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "blue",  "set blue points coordinates",  OFFSET(comp_points_str[2]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "b",     "set blue points coordinates",  OFFSET(comp_points_str[2]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(curves);
+
+static struct keypoint *make_point(double x, double y, struct keypoint *next)
+{
+    struct keypoint *point = av_mallocz(sizeof(*point));
+
+    if (!point)
+        return NULL;
+    point->x = x;
+    point->y = y;
+    point->next = next;
+    return point;
+}
+
+static int parse_points_str(AVFilterContext *ctx, struct keypoint **points, const char *s)
+{
+    char *p = (char *)s; // strtod won't alter the string
+    struct keypoint *last = NULL;
+
+    /* construct a linked list based on the key points string */
+    while (p && *p) {
+        struct keypoint *point = make_point(0, 0, NULL);
+        if (!point)
+            return AVERROR(ENOMEM);
+        point->x = av_strtod(p, &p); if (p && *p) p++;
+        point->y = av_strtod(p, &p); if (p && *p) p++;
+        if (point->x < 0 || point->x > 1 || point->y < 0 || point->y > 1) {
+            av_log(ctx, AV_LOG_ERROR, "Invalid key point coordinates (%f;%f), "
+                   "x and y must be in the [0;1] range.\n", point->x, point->y);
+            return AVERROR(EINVAL);
+        }
+        if (!*points)
+            *points = point;
+        if (last) {
+            if ((int)(last->x * 255) >= (int)(point->x * 255)) {
+                av_log(ctx, AV_LOG_ERROR, "Key point coordinates (%f;%f) "
+                       "and (%f;%f) are too close from each other or not "
+                       "strictly increasing on the x-axis\n",
+                       last->x, last->y, point->x, point->y);
+                return AVERROR(EINVAL);
+            }
+            last->next = point;
+        }
+        last = point;
+    }
+
+    /* auto insert first key point if missing at x=0 */
+    if (!*points) {
+        last = make_point(0, 0, NULL);
+        if (!last)
+            return AVERROR(ENOMEM);
+        last->x = last->y = 0;
+        *points = last;
+    } else if ((*points)->x != 0.) {
+        struct keypoint *newfirst = make_point(0, 0, *points);
+        if (!newfirst)
+            return AVERROR(ENOMEM);
+        *points = newfirst;
+    }
+
+    av_assert0(last);
+
+    /* auto insert last key point if missing at x=1 */
+    if (last->x != 1.) {
+        struct keypoint *point = make_point(1, 1, NULL);
+        if (!point)
+            return AVERROR(ENOMEM);
+        last->next = point;
+    }
+
+    return 0;
+}
+
+static int get_nb_points(const struct keypoint *d)
+{
+    int n = 0;
+    while (d) {
+        n++;
+        d = d->next;
+    }
+    return n;
+}
+
+/**
+ * Natural cubic spline interpolation
+ * Finding curves using Cubic Splines notes by Steven Rauch and John Stockie.
+ * @see http://people.math.sfu.ca/~stockie/teaching/macm316/notes/splines.pdf
+ */
+static int interpolate(AVFilterContext *ctx, uint8_t *y, const struct keypoint *points)
+{
+    int i, ret = 0;
+    const struct keypoint *point;
+    double xprev = 0;
+
+    int n = get_nb_points(points); // number of splines
+
+    double (*matrix)[3] = av_calloc(n, sizeof(*matrix));
+    double *h = av_malloc((n - 1) * sizeof(*h));
+    double *r = av_calloc(n, sizeof(*r));
+
+    if (!matrix || !h || !r) {
+        ret = AVERROR(ENOMEM);
+        goto end;
+    }
+
+    /* h(i) = x(i+1) - x(i) */
+    i = -1;
+    for (point = points; point; point = point->next) {
+        if (i != -1)
+            h[i] = point->x - xprev;
+        xprev = point->x;
+        i++;
+    }
+
+    /* right-side of the polynomials, will be modified to contains the solution */
+    point = points;
+    for (i = 1; i < n - 1; i++) {
+        double yp = point->y,
+               yc = point->next->y,
+               yn = point->next->next->y;
+        r[i] = 6 * ((yn-yc)/h[i] - (yc-yp)/h[i-1]);
+        point = point->next;
+    }
+
+#define B 0 /* sub  diagonal (below main) */
+#define M 1 /* main diagonal (center) */
+#define A 2 /* sup  diagonal (above main) */
+
+    /* left side of the polynomials into a tridiagonal matrix. */
+    matrix[0][M] = matrix[n - 1][M] = 1;
+    for (i = 1; i < n - 1; i++) {
+        matrix[i][B] = h[i-1];
+        matrix[i][M] = 2 * (h[i-1] + h[i]);
+        matrix[i][A] = h[i];
+    }
+
+    /* tridiagonal solving of the linear system */
+    for (i = 1; i < n; i++) {
+        double den = matrix[i][M] - matrix[i][B] * matrix[i-1][A];
+        double k = den ? 1./den : 1.;
+        matrix[i][A] *= k;
+        r[i] = (r[i] - matrix[i][B] * r[i - 1]) * k;
+    }
+    for (i = n - 2; i >= 0; i--)
+        r[i] = r[i] - matrix[i][A] * r[i + 1];
+
+    /* compute the graph with x=[0..255] */
+    i = 0;
+    point = points;
+    av_assert0(point->next); // always at least 2 key points
+    while (point->next) {
+        double yc = point->y;
+        double yn = point->next->y;
+
+        double a = yc;
+        double b = (yn-yc)/h[i] - h[i]*r[i]/2. - h[i]*(r[i+1]-r[i])/6.;
+        double c = r[i] / 2.;
+        double d = (r[i+1] - r[i]) / (6.*h[i]);
+
+        int x;
+        int x_start = point->x       * 255;
+        int x_end   = point->next->x * 255;
+
+        av_assert0(x_start >= 0 && x_start <= 255 &&
+                   x_end   >= 0 && x_end   <= 255);
+
+        for (x = x_start; x <= x_end; x++) {
+            double xx = (x - x_start) * 1/255.;
+            double yy = a + b*xx + c*xx*xx + d*xx*xx*xx;
+            y[x] = av_clipf(yy, 0, 1) * 255;
+            av_log(ctx, AV_LOG_DEBUG, "f(%f)=%f -> y[%d]=%d\n", xx, yy, x, y[x]);
+        }
+
+        point = point->next;
+        i++;
+    }
+
+end:
+    av_free(matrix);
+    av_free(h);
+    av_free(r);
+    return ret;
+}
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+    int i, j, ret;
+    CurvesContext *curves = ctx->priv;
+    struct keypoint *comp_points[NB_COMP] = {0};
+
+    curves->class = &curves_class;
+    av_opt_set_defaults(curves);
+
+    if ((ret = av_set_options_string(curves, args, "=", ":")) < 0)
+        return ret;
+
+    for (i = 0; i < NB_COMP; i++) {
+        ret = parse_points_str(ctx, comp_points + i, curves->comp_points_str[i]);
+        if (ret < 0)
+            return ret;
+        ret = interpolate(ctx, curves->graph[i], comp_points[i]);
+        if (ret < 0)
+            return ret;
+    }
+
+    if (av_log_get_level() >= AV_LOG_VERBOSE) {
+        for (i = 0; i < NB_COMP; i++) {
+            struct keypoint *point = comp_points[i];
+            av_log(ctx, AV_LOG_VERBOSE, "#%d points:", i);
+            while (point) {
+                av_log(ctx, AV_LOG_VERBOSE, " (%f;%f)", point->x, point->y);
+                point = point->next;
+            }
+            av_log(ctx, AV_LOG_VERBOSE, "\n");
+            av_log(ctx, AV_LOG_VERBOSE, "#%d values:", i);
+            for (j = 0; j < 256; j++)
+                av_log(ctx, AV_LOG_VERBOSE, " %02X", curves->graph[i][j]);
+            av_log(ctx, AV_LOG_VERBOSE, "\n");
+        }
+    }
+
+    for (i = 0; i < NB_COMP; i++) {
+        struct keypoint *point = comp_points[i];
+        while (point) {
+            struct keypoint *next = point->next;
+            av_free(point);
+            point = next;
+        }
+    }
+
+    av_opt_free(curves);
+    return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {AV_PIX_FMT_RGB24, AV_PIX_FMT_NONE};
+    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    int x, y, i, direct = 0;
+    AVFilterContext *ctx = inlink->dst;
+    CurvesContext *curves = ctx->priv;
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+    AVFrame *out;
+    uint8_t *dst;
+    const uint8_t *src;
+
+    if (av_frame_is_writable(in)) {
+        direct = 1;
+        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);
+    }
+
+    dst = out->data[0];
+    src = in ->data[0];
+
+    for (y = 0; y < inlink->h; y++) {
+        uint8_t *dstp = dst;
+        const uint8_t *srcp = src;
+
+        for (x = 0; x < inlink->w; x++)
+            for (i = 0; i < NB_COMP; i++, dstp++, srcp++)
+                *dstp = curves->graph[i][*srcp];
+        dst += out->linesize[0];
+        src += in ->linesize[0];
+    }
+
+    if (!direct)
+        av_frame_free(&in);
+
+    return ff_filter_frame(outlink, out);
+}
+
+static const AVFilterPad curves_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad curves_outputs[] = {
+     {
+         .name = "default",
+         .type = AVMEDIA_TYPE_VIDEO,
+     },
+     { NULL }
+};
+
+AVFilter avfilter_vf_curves = {
+    .name          = "curves",
+    .description   = NULL_IF_CONFIG_SMALL("Adjust components curves."),
+    .priv_size     = sizeof(CurvesContext),
+    .init          = init,
+    .query_formats = query_formats,
+    .inputs        = curves_inputs,
+    .outputs       = curves_outputs,
+    .priv_class    = &curves_class,
+};