[FFmpeg-devel] [PATCH v2 4/4] avfilter/vf_drawbox: support draw specific face by facedetect metadata

[lance.lmwang at gmail.com]

On Wed, May 13, 2020 at 07:16:47PM +0200, Marton Balint wrote:
> 
> 
> On Wed, 13 May 2020, lance.lmwang at gmail.com wrote:
> 
> > From: Limin Wang <lance.lmwang at gmail.com>
> > 
> > Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> > ---
> > doc/filters.texi         | 10 ++++++++++
> > libavfilter/vf_drawbox.c | 27 +++++++++++++++++++++++++++
> > 2 files changed, 37 insertions(+)
> > 
> > diff --git a/doc/filters.texi b/doc/filters.texi
> > index 76e12ef..bf9043c 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -9337,6 +9337,10 @@ See below for the list of accepted constants.
> > Applicable if the input has alpha. With value @code{1}, the pixels of the painted box
> > will overwrite the video's color and alpha pixels.
> > Default is @code{0}, which composites the box onto the input, leaving the video's alpha intact.
> > +
> > + at item face
> > +Draw the box by the facedetect metadata for the specific face.
> 
> @item face @var{integer}
> Draw the box onto the position of the nth face as detected by the ocv
> filter's facedetect mode. If no face detection metadata exists
> then the filter will use the specified box parameters instead.
thanks, it's more clear, will update.

> 
> > +
> > @end table
> > 
> > The parameters for @var{x}, @var{y}, @var{w} and @var{h} and @var{t} are expressions containing the
> > @@ -9405,6 +9409,12 @@ Draw a 2-pixel red 2.40:1 mask:
> > @example
> > drawbox=x=-t:y=0.5*(ih-iw/2.4)-t:w=iw+t*2:h=iw/2.4+t*2:t=2:c=red
> > @end example
> > +
> > + at item
> > +draw the box with red color for the first face by metadata if its postion is detected:
> 
> Draw a red box onto the position of the first face as detected by the ocv
> filter's facedetect method.
will updat

> 
> > + at example
> > +ocv=filter_name=facedetect:filter_params=facedetect=./haarcascade_frontalface_alt.xml,drawbox=face=0:color=red
> > + at end example
> > @end itemize
> > 
> > @subsection Commands
> > diff --git a/libavfilter/vf_drawbox.c b/libavfilter/vf_drawbox.c
> > index 21d520e..239a149 100644
> > --- a/libavfilter/vf_drawbox.c
> > +++ b/libavfilter/vf_drawbox.c
> > @@ -81,6 +81,7 @@ typedef struct DrawBoxContext {
> >     char *t_expr;          ///< expression for thickness
> >     int have_alpha;
> >     int replace;
> > +    int face;
> > } DrawBoxContext;
> > 
> > static const int NUM_EXPR_EVALS = 5;
> > @@ -220,6 +221,31 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
> >     int plane, x, y, xb = s->x, yb = s->y;
> >     unsigned char *row[4];
> > 
> > +    if (s->face >= 0) {
> > +        AVDictionaryEntry *ex, *ey, *ew, *eh;
> > +        char key2[128];
> > +        AVDictionary *metadata = frame->metadata;
> > +
> > +        snprintf(key2, sizeof(key2), "lavfi.facedetect.%d.%s", s->face, "x");
> > +        ex = av_dict_get(metadata, key2, NULL, AV_DICT_MATCH_CASE);
> > +
> > +        snprintf(key2, sizeof(key2), "lavfi.facedetect.%d.%s", s->face, "y");
> > +        ey = av_dict_get(metadata, key2, NULL, AV_DICT_MATCH_CASE);
> > +
> > +        snprintf(key2, sizeof(key2), "lavfi.facedetect.%d.%s", s->face, "w");
> > +        ew = av_dict_get(metadata, key2, NULL, AV_DICT_MATCH_CASE);
> > +
> > +        snprintf(key2, sizeof(key2), "lavfi.facedetect.%d.%s", s->face, "h");
> > +        eh = av_dict_get(metadata, key2, NULL, AV_DICT_MATCH_CASE);
> > +
> > +        if (ex && ey && ew && eh) {
> > +            xb = s->x = strtol(ex->value, NULL, 10);
> > +            yb = s->y = strtol(ey->value, NULL, 10);
> > +            s->w = strtol(ew->value, NULL, 10);
> > +            s->h = strtol(eh->value, NULL, 10);
> > +        }
> > +    }
> > +
> >     if (s->have_alpha && s->replace) {
> >         for (y = FFMAX(yb, 0); y < frame->height && y < (yb + s->h); y++) {
> >             row[0] = frame->data[0] + y * frame->linesize[0];
> > @@ -323,6 +349,7 @@ static const AVOption drawbox_options[] = {
> >     { "thickness", "set the box thickness",                        OFFSET(t_expr),    AV_OPT_TYPE_STRING, { .str="3" },       0, 0, FLAGS },
> >     { "t",         "set the box thickness",                        OFFSET(t_expr),    AV_OPT_TYPE_STRING, { .str="3" },       0, 0, FLAGS },
> >     { "replace",   "replace color & alpha",                        OFFSET(replace),   AV_OPT_TYPE_BOOL,   { .i64=0 },         0,        1,        FLAGS },
> > +    { "face",      "set which face to draw with metadata",         OFFSET(face),      AV_OPT_TYPE_INT,    { .i64=-1 },        -1,     256,        FLAGS },
> >     { NULL }
> > };
> > 
> 
> It is a bit more work, but have you considered making the face position
> available to the filter as a variable to the expressions? Also possibly you
> could add a new mode to the filter to select when to evaluate the
> x/y/width/height/tickness parameters, at initalization time, or for each
> frame. Several filters alrady have such selectors (e.g.: see the the eval
> parameter of vf_eq).
> 
> I don't oppose the patch as is, but it is something worth considering.

It's good idea, I'm considering to add opencv drawbox filter, for now, 
I prefer to keep the change simple for this stage. I'll do more in future.


> 
> Regards,
> Marton
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-- 
Thanks,
Limin Wang