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

Paul B Mahol onemda at gmail.com
Tue Mar 5 18:53:14 CET 2013


On 3/5/13, Clement Boesch <ubitux at gmail.com> wrote:
> 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

Mentioning those two does not explain in simple terms what filter actually does.

> +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.

typo: s/red/blue.

nit+++++++++++++: Isn't it more logical to put shorter name after longer one?

> + 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 Clement Boesch
> + *
> + * 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
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>


More information about the ffmpeg-devel mailing list