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

[Ramiro Polla]

On Thu, Jan 9, 2014 at 12:42 PM, Ramiro Polla <ramiro.polla at gmail.com> wrote:
> On Thu, Jan 9, 2014 at 8:26 AM, Stefano Sabatini <stefasab at gmail.com> wrote:
>> 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.
>
> Indeed, it is more complicated implementation-wise. There is also the
> option of using the FreeType stroker, but that library has a horrible
> API and the examples are confusing, so I couldn't get it to work.

Got it! New patches sent.