[FFmpeg-devel] [PATCH] lavfi/drawtext: add option for drawing border around text

[Stefano Sabatini]

On date Thursday 2014-01-09 00:13:37 -0200, Ramiro Polla encoded:
> 

> From 52b6cda0ee5bfaf6e594eb5a7923be00eac575d8 Mon Sep 17 00:00:00 2001
> From: Ramiro Polla <ramiro.polla at gmail.com>
> Date: Thu, 9 Jan 2014 00:05:43 -0200
> Subject: [PATCH] lavfi/drawtext: add option for drawing border around text
> 
> ---
>  doc/filters.texi          |   11 +++++++++++
>  libavfilter/vf_drawtext.c |   15 +++++++++++++++
>  2 files changed, 26 insertions(+)

This feature was implemented in the original VHOOK drawtext filter
(was named "outline"). Since the rendering result was pretty poor I
decided to drop it.

> diff --git a/doc/filters.texi b/doc/filters.texi
> index c896edb..9f97dc0 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -3548,6 +3548,17 @@ option, check the "Color" section in the ffmpeg-utils manual.
>  
>  The default value of @var{boxcolor} is "white".
>  
> + at item border
> +Used to draw a 1-pixel-thick border around text using @var{bordercolor}.
> +Value should be either 1 (enable) or 0 (disable).
> +The default value of @var{border} is 0.
> +
> + at item bordercolor
> +The color to be used for drawing border around text. For the syntax of this
> +option, check the "Color" section in the ffmpeg-utils manual.
> +
> +The default value of @var{bordercolor} is "black".
> +
>  @item expansion
>  Select how the @var{text} is expanded. Can be either @code{none},
>  @code{strftime} (deprecated) or
> diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
> index 91b8218..c14bac3 100644
> --- a/libavfilter/vf_drawtext.c
> +++ b/libavfilter/vf_drawtext.c
> @@ -136,6 +136,7 @@ typedef struct {
>      int shadowx, shadowy;
>      unsigned int fontsize;          ///< font size to use
>  
> +    short int draw_border;          ///< draw border around text - true or false
>      short int draw_box;             ///< draw box around text - true or false
>      int use_kerning;                ///< font kerning is used - true/false
>      int tabsize;                    ///< tab size
> @@ -144,6 +145,7 @@ typedef struct {
>      FFDrawContext dc;
>      FFDrawColor fontcolor;          ///< foreground color
>      FFDrawColor shadowcolor;        ///< shadow color
> +    FFDrawColor bordercolor;        ///< border color
>      FFDrawColor boxcolor;           ///< background color
>  
>      FT_Library library;             ///< freetype font library handle
> @@ -179,6 +181,8 @@ static const AVOption drawtext_options[]= {
>      {"fontcolor",   "set foreground color", OFFSET(fontcolor.rgba),     AV_OPT_TYPE_COLOR,  {.str="black"}, CHAR_MIN, CHAR_MAX, FLAGS},
>      {"boxcolor",    "set box color",        OFFSET(boxcolor.rgba),      AV_OPT_TYPE_COLOR,  {.str="white"}, CHAR_MIN, CHAR_MAX, FLAGS},
>      {"shadowcolor", "set shadow color",     OFFSET(shadowcolor.rgba),   AV_OPT_TYPE_COLOR,  {.str="black"}, CHAR_MIN, CHAR_MAX, FLAGS},
> +    {"bordercolor", "set border color",     OFFSET(bordercolor.rgba),   AV_OPT_TYPE_COLOR,  {.str="black"}, CHAR_MIN, CHAR_MAX, FLAGS},
> +    {"border",      "set border",           OFFSET(draw_border),        AV_OPT_TYPE_INT,    {.i64=0},     0,        1       , FLAGS},
>      {"box",         "set box",              OFFSET(draw_box),           AV_OPT_TYPE_INT,    {.i64=0},     0,        1       , FLAGS},
>      {"fontsize",    "set font size",        OFFSET(fontsize),           AV_OPT_TYPE_INT,    {.i64=0},     0,        INT_MAX , FLAGS},
>      {"x",           "set x expression",     OFFSET(x_expr),             AV_OPT_TYPE_STRING, {.str="0"},   CHAR_MIN, CHAR_MAX, FLAGS},
> @@ -559,6 +563,7 @@ static int config_input(AVFilterLink *inlink)
>      ff_draw_init(&s->dc, inlink->format, 0);
>      ff_draw_color(&s->dc, &s->fontcolor,   s->fontcolor.rgba);
>      ff_draw_color(&s->dc, &s->shadowcolor, s->shadowcolor.rgba);
> +    ff_draw_color(&s->dc, &s->bordercolor, s->bordercolor.rgba);
>      ff_draw_color(&s->dc, &s->boxcolor,    s->boxcolor.rgba);
>  
>      s->var_values[VAR_w]     = s->var_values[VAR_W]     = s->var_values[VAR_MAIN_W] = inlink->w;
> @@ -995,6 +1000,16 @@ static int draw_text(AVFilterContext *ctx, AVFrame *frame,
>                             frame->data, frame->linesize, width, height,
>                             s->x, s->y, box_w, box_h);
>  

> +    if (s->draw_border) {
> +        int offsets[4][2] = { { -1, -1 }, { -1, +1 }, { +1, -1 }, { +1, +1 } };
> +        for (i = 0; i < 4; i++) {
> +            ret = draw_glyphs(s, frame, width, height, s->bordercolor.rgba,
> +                              &s->bordercolor, offsets[i][0], offsets[i][1]);
> +            if (ret < 0)
> +                return ret;
> +        }
> +    }

This will require printing the glyphs four times, which is not very
efficient. Alternatively you could implement a system like the one in
the VHOOK filter, which would be faster but more complicate
implementation-wise.

Do you have any specific reason for wanting to implment such a
feature?
-- 
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