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

Nicolas George nicolas.george at normalesup.org
Tue Mar 5 19:27:43 CET 2013


Le quintidi 15 ventôse, an CCXXI, Clement Boesch a écrit :
> 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 {

In the docs, you use the word "point", to my non-native ear it sounds more
correct in this case.

> +    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];

The key points are only used during the init: you can make it a local
variable.

> +    uint8_t graph[NB_COMP*256];

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;
> +}

This is very inefficient, both in speed and in memory, and even more in
needs of error checks. Since there is a hard limit of 256 on the number of
control points, what about a simple array?

double dots[256][2];
unsigned nb_dots = 0;

> +
> +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;

When building linked lists, keeping a pointer to the next field of the list
tail makes the code a little simpler:

struct keydot **tail = dots;
***
    *tail = dot;
    tail = &dot->next;

> +
> +    /* 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++;

You are not checking the delimiter, which may be fine.

> +        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)) {

If you keep a single variable "double last_x = -1", you can omit the
"if(last)" test.

> +                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;
> +    }

This part can certainly be simplified, but it depends on the actual data
structure used.

Right now, I would suggest to insert the last point first.

> +
> +    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)

I will look at the maths later.

<snip>

> +
> +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++)

s/3/NB_COMP/

> +                p[i] = curves->graph[p[i] + i*256];
> +            p += i;

Why not "p++" in the inner loop?

> +        }
> +        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,
> +};

Regards,

-- 
  Nicolas George
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