[FFmpeg-devel] [PATCH] lavfi: add curves filter.

Clément Bœsch ubitux at gmail.com
Tue Mar 5 18:09:26 CET 2013


TODO: bump minor
---
pseudo-vintage/matrix effect: http://imgur.com/w8sQ4gw
Obtained with:
  mp=eq2=1:1.2,
  hue=h=20,
  curves=r='0.4/0.2 0.9/1':g='0.75/0.8':b='0/0.1 1/0.9'
---
 doc/filters.texi         |  64 +++++++++
 libavfilter/Makefile     |   1 +
 libavfilter/allfilters.c |   1 +
 libavfilter/vf_curves.c  | 345 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 411 insertions(+)
 create mode 100644 libavfilter/vf_curves.c

diff --git a/doc/filters.texi b/doc/filters.texi
index f4c1d03..e97e974 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -2187,6 +2187,70 @@ indicates never reset and return the largest area encountered during
 playback.
 @end table
 
+ at 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.
+
+By default, a component curve is defined by the two points @var{(0;0)} and
+ at 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.
+
+ at table @option
+ at item r, red
+Set the key points for the red components.
+ at item g, green
+Set the key points for the green components.
+ at item b, blue
+Set the key points for the red components.
+ at 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 ...}.
+
+ at subsection Examples
+ at itemize
+ at item
+Increase slightly the middle level of blue:
+ at example
+curves=b='0.5/0.58'
+ at end example
+
+ at item
+Pseudo-vintage effect:
+ at example
+curves=r='0.4/0.2 0.9/1':g='0.75/0.8':b='0/0.1 1/0.9'
+ at end example
+Here we obtain the following coordinates for each components:
+ at table @var
+ at item red
+ at code{(0;0) (0.4;0.2) (0.9;1) (1;1)}
+ at item green
+ at code{(0;0) (0.75;0.8) (1;1)}
+ at item blue
+ at code{(0;0.1) (1;0.9)}
+ at end table
+ at end itemize
+
 @section decimate
 
 Drop frames that do not differ greatly from the previous frame in
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 04ed8b8..d6a1eb4 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -106,6 +106,7 @@ 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
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index f05f8ae..14783a7 100644
--- a/libavfilter/allfilters.c
+++ b/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);
diff --git a/libavfilter/vf_curves.c b/libavfilter/vf_curves.c
new file mode 100644
index 0000000..81c0fcb
--- /dev/null
+++ b/libavfilter/vf_curves.c
@@ -0,0 +1,345 @@
+/*
+ * 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 keydot {
+    double x, y;
+    struct keydot *next;
+};
+
+#define NB_COMP 3
+
+typedef struct {
+    const AVClass *class;
+    char *comp_dots_str[NB_COMP];
+    struct keydot *comp_dots[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[] = {
+    { "r",     "set red dots coordinates",   OFFSET(comp_dots_str[0]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "red",   "set red dots coordinates",   OFFSET(comp_dots_str[0]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "g",     "set green dots coordinates", OFFSET(comp_dots_str[1]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "green", "set green dots coordinates", OFFSET(comp_dots_str[1]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "b",     "set blue dots coordinates",  OFFSET(comp_dots_str[2]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { "blue",  "set blue dots coordinates",  OFFSET(comp_dots_str[2]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(curves);
+
+static struct keydot *new_dot(double x, double y, struct keydot *next)
+{
+    struct keydot *dot = av_mallocz(sizeof(*dot));
+
+    if (!dot)
+        return NULL;
+    dot->x = x;
+    dot->y = y;
+    dot->next = next;
+    return dot;
+}
+
+static int parse_dots_str(AVFilterContext *ctx, struct keydot **dots, const char *s)
+{
+    char *p = (char *)s; // strtod won't alter the string
+    struct keydot *last = NULL;
+
+    /* construct a linked list based on the key dots string */
+    while (p && *p) {
+        struct keydot *dot = new_dot(0, 0, NULL);
+        if (!dot)
+            return AVERROR(ENOMEM);
+        dot->x = av_strtod(p, &p); if (p && *p) p++;
+        dot->y = av_strtod(p, &p); if (p && *p) p++;
+        if (dot->x < 0 || dot->x > 1 || dot->y < 0 || dot->y > 1) {
+            av_log(ctx, AV_LOG_ERROR, "Invalid key dot coordinates (%f;%f), "
+                   "x and y must be in the [0;1] range.\n", dot->x, dot->y);
+            return AVERROR(EINVAL);
+        }
+        if (!*dots)
+            *dots = dot;
+        if (last) {
+            if ((int)(last->x * 255) >= (int)(dot->x * 255)) {
+                av_log(ctx, AV_LOG_WARNING, "Key dot coordinates (%f;%f) "
+                       "and (%f;%f) are too close from each other on the "
+                       "x-axis\n", last->x, last->y, dot->x, dot->y);
+                return AVERROR(EINVAL);
+            }
+            last->next = dot;
+        }
+        last = dot;
+    }
+
+    /* auto insert first key dot if missing at x=0 */
+    if (!*dots) {
+        last = new_dot(0, 0, NULL);
+        if (!last)
+            return AVERROR(ENOMEM);
+        last->x = last->y = 0;
+        *dots = last;
+    } else if ((*dots)->x != 0.) {
+        struct keydot *newfirst = new_dot(0, 0, *dots);
+        if (!newfirst)
+            return AVERROR(ENOMEM);
+        *dots = newfirst;
+    }
+
+    av_assert0(last);
+
+    /* auto insert last key dot if missing at x=1 */
+    if (last->x != 1.) {
+        struct keydot *dot = new_dot(1, 1, NULL);
+        if (!dot)
+            return AVERROR(ENOMEM);
+        last->next = dot;
+    }
+
+    return 0;
+}
+
+static int get_nb_dots(const struct keydot *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 keydot *dots)
+{
+    int i, ret = 0;
+    const struct keydot *dot;
+    double xprev = 0;
+
+    int n = get_nb_dots(dots); // number of splines
+
+    double *matrix = av_calloc(3 * 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 (dot = dots; dot; dot = dot->next) {
+        if (i != -1)
+            h[i] = dot->x - xprev;
+        xprev = dot->x;
+        i++;
+    }
+
+    /* right-side of the polynomials, will be modified to contains the solution */
+    dot = dots;
+    for (i = 1; i < n - 1; i++) {
+        double yp = dot->y,
+               yc = dot->next->y,
+               yn = dot->next->next->y;
+        r[i] = 6 * ((yn-yc)/h[i] - (yc-yp)/h[i-1]);
+        dot = dot->next;
+    }
+
+    /* left side of the polynomials into a tridiagonal matrix */
+    matrix[0] = matrix[n*3 - 1] = 1;
+    for (i = 1; i < n - 1; i++) {
+        matrix[i*3    ] = h[i-1];
+        matrix[i*3 + 1] = 2 * (h[i-1] + h[i]);
+        matrix[i*3 + 2] = h[i];
+    }
+
+    /* tridiagonal solving of the linear system */
+    for (i = 1; i < n; i++) {
+        double den = matrix[i*3 + 1] - matrix[i*3] * matrix[(i-1)*3 + 2];
+        double k = den ? 1./den : 1.;
+        matrix[i*3 + 2] *= k;
+        r[i] = (r[i] - matrix[i*3] * r[i - 1]) * k;
+    }
+    for (i = n - 2; i >= 0; i--)
+        r[i] = r[i] - matrix[i*3 + 2] * r[i + 1];
+
+    /* compute the graph with x=[0..255] */
+    i = 0;
+    dot = dots;
+    av_assert0(dot->next); // always at least 2 key points
+    while (dot->next) {
+        double yc = dot->y;
+        double yn = dot->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 = dot->x       * 255;
+        int x_end   = dot->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]);
+        }
+
+        dot = dot->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;
+
+    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_dots_str(ctx, curves->comp_dots + i, curves->comp_dots_str[i]);
+        if (ret < 0)
+            return ret;
+        ret = interpolate(ctx, curves->graph + 256*i, curves->comp_dots[i]);
+        if (ret < 0)
+            return ret;
+    }
+
+    if (av_log_get_level() >= AV_LOG_VERBOSE) {
+        for (i = 0; i < NB_COMP; i++) {
+            struct keydot *dot = curves->comp_dots[i];
+            av_log(ctx, AV_LOG_VERBOSE, "#%d dots:", i);
+            while (dot) {
+                av_log(ctx, AV_LOG_VERBOSE, " (%f;%f)", dot->x, dot->y);
+                dot = dot->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*256 + j]);
+            av_log(ctx, AV_LOG_VERBOSE, "\n");
+        }
+    }
+
+    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, AVFilterBufferRef *in)
+{
+    int x, y, i;
+    AVFilterContext *ctx = inlink->dst;
+    CurvesContext *curves = ctx->priv;
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+    uint8_t *dst = in->data[0];
+
+    for (y = 0; y < inlink->h; y++) {
+        uint8_t *p = dst;
+        for (x = 0; x < inlink->w; x++) {
+            for (i = 0; i < 3; i++)
+                p[i] = curves->graph[p[i] + i*256];
+            p += i;
+        }
+        dst += in->linesize[0];
+    }
+    return ff_filter_frame(outlink, in);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    int i;
+    CurvesContext *curves = ctx->priv;
+
+    for (i = 0; i < FF_ARRAY_ELEMS(curves->comp_dots_str); i++) {
+        struct keydot *dot = curves->comp_dots[i];
+        while (dot) {
+            struct keydot *next = dot->next;
+            av_free(dot);
+            dot = next;
+        }
+    }
+
+    av_opt_free(curves);
+}
+
+static const AVFilterPad curves_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+        .min_perms    = AV_PERM_WRITE,
+     },
+     { 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,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+    .inputs        = curves_inputs,
+    .outputs       = curves_outputs,
+    .priv_class    = &curves_class,
+};
-- 
1.8.1.5



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