On Wed, 13 May 2020, lance.lmw...@gmail.com wrote:
From: Limin Wang <lance.lmw...@gmail.com>
Signed-off-by: Limin Wang <lance.lmw...@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.
+
+@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.
+
@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
+
+@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.
+@example
+ocv=filter_name=facedetect:filter_params=facedetect=./haarcascade_frontalface_alt.xml,drawbox=face=0:color=red
+@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.
Regards,
Marton
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