[FFmpeg-devel] [PATCH] libavfilter/vf_drawtext:support to set glyph spacing while drawing text.

[Michael Niedermayer]

On Fri, Jul 21, 2017 at 11:35:14AM +0800, efren yang wrote:
> It is applied to every glyph. There is no space between all words in some languages, for example Chinese, Japanese and so on. So a sentence will look very compactly. I think if we could set glyph spacing, it will adapt to more different scenarios. Maybe it is simple but useful.
> 
> ffmpeg -i input -vf    drawtext="glyph_spacing=10:text="PROGRAMMING":fontfile=demo.ttf" -f flv 1.flv could set glyph spacing 10 pixel.
> 
> Signed-off-by: efren yang <efren_yang at 163.com>
> ---
>  doc/filters.texi          | 4 ++++
>  libavfilter/vf_drawtext.c | 3 +++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 119d1be69d..0f336f8826 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -7077,6 +7077,10 @@ The default value of @var{boxcolor} is "white".
>  Set the line spacing in pixels of the border to be drawn around the box using @var{box}.
>  The default value of @var{line_spacing} is 0.
>  
> + at item glyph_spacing
> +Set the glyph spacing in pixels for drawing text.
> +The default value of @var{glyph_spacing} is 0.
> +
>  @item borderw
>  Set the width of the border to be drawn around the text using @var{bordercolor}.
>  The default value of @var{borderw} is 0.
> diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
> index f6151443bb..152d8f35d5 100644
> --- a/libavfilter/vf_drawtext.c
> +++ b/libavfilter/vf_drawtext.c
> @@ -162,6 +162,7 @@ typedef struct DrawTextContext {
>      unsigned int default_fontsize;  ///< default font size to use
>  
>      int line_spacing;               ///< lines spacing in pixels
> +    int glyph_spacing;              ///< glyph spacing in pixels
>      short int draw_box;             ///< draw box around text - true or false
>      int boxborderw;                 ///< box border width
>      int use_kerning;                ///< font kerning is used - true/false
> @@ -214,6 +215,7 @@ static const AVOption drawtext_options[]= {
>      {"box",         "set box",              OFFSET(draw_box),           AV_OPT_TYPE_BOOL,   {.i64=0},     0,        1       , FLAGS},
>      {"boxborderw",  "set box border width", OFFSET(boxborderw),         AV_OPT_TYPE_INT,    {.i64=0},     INT_MIN,  INT_MAX , FLAGS},
>      {"line_spacing",  "set line spacing in pixels", OFFSET(line_spacing),   AV_OPT_TYPE_INT,    {.i64=0},     INT_MIN,  INT_MAX,FLAGS},
> +    {"glyph_spacing",  "set glyph spacing in pixels", OFFSET(glyph_spacing),   AV_OPT_TYPE_INT,    {.i64 = 0},     0,  INT_MAX,FLAGS },
>      {"fontsize",    "set font size",        OFFSET(fontsize_expr),      AV_OPT_TYPE_STRING, {.str=NULL},  CHAR_MIN, CHAR_MAX , FLAGS},
>      {"x",           "set x expression",     OFFSET(x_expr),             AV_OPT_TYPE_STRING, {.str="0"},   CHAR_MIN, CHAR_MAX, FLAGS},
>      {"y",           "set y expression",     OFFSET(y_expr),             AV_OPT_TYPE_STRING, {.str="0"},   CHAR_MIN, CHAR_MAX, FLAGS},
> @@ -1374,6 +1376,7 @@ static int draw_text(AVFilterContext *ctx, AVFrame *frame,
>          s->positions[i].y = y - glyph->bitmap_top + y_max;
>          if (code == '\t') x  = (x / s->tabsize + 1)*s->tabsize;
>          else              x += glyph->advance;
> +        x += s->glyph_spacing;

This still needs a  check
glyph_spacing is just checked against INT_MAX and x is a int so
if x is > 0 this would be undefined and even if defined it would be
wrong

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

What does censorship reveal? It reveals fear. -- Julian Assange
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