[FFmpeg-devel] [PATCH] libavfilter/vf_drawtext: add letter_spacing as an evaluated parameter
Francesco Carusi
klimklim at tiscali.it
Tue Jun 20 17:27:31 EEST 2023
You can find an overview of the changes here:
https://github.com/yethie/FFmpeg/blob/master/drawtext/CHANGES.md
and the new code here:
https://github.com/yethie/FFmpeg/blob/master/libavfilter/vf_drawtext.c
On 19/06/2023 19:56, Mark Ren wrote:
> Ah alright I see. When might that push come through and is there somewhere
> I can look at the kind of changes in the meantime?
>
> On Mon, Jun 19, 2023 at 12:39 PM Paul B Mahol <onemda at gmail.com> wrote:
>
>>
>> On Mon, Jun 19, 2023 at 6:34 PM Mark Ren <mark.ren77 at gmail.com> wrote:
>>
>>> When enabled it will add pixels (or subtract if given a negative value)
>>> between each letters,
>>> set use_kerning to false,
>>> and add the pixels to text_w.
>>>
>> Conflicts with big drawtext filter set that will be pushed soon.
>>
>>
>>> Signed-off-by: Mark Ren <mark.ren77 at gmail.com>
>>> ---
>>> libavfilter/vf_drawtext.c | 24 ++++++++++++++++++++----
>>> 1 file changed, 20 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
>>> index 71ab851462..ec8313820d 100644
>>> --- a/libavfilter/vf_drawtext.c
>>> +++ b/libavfilter/vf_drawtext.c
>>> @@ -183,6 +183,7 @@ typedef struct DrawTextContext {
>>> unsigned int fontsize; ///< font size to use
>>> unsigned int default_fontsize; ///< default font size to use
>>>
>>> + int letter_spacing; ///< letter spacing in pixels
>>> int line_spacing; ///< lines spacing in pixels
>>> short int draw_box; ///< draw box around text - true or
>>> false
>>> int boxborderw; ///< box border width
>>> @@ -208,6 +209,8 @@ typedef struct DrawTextContext {
>>> char *a_expr;
>>> AVExpr *a_pexpr;
>>> int alpha;
>>> + char* letter_spacing_expr; ///< expression for letter spacing
>>> + AVExpr* letter_spacing_pexpr; ///< parsed expression for letter
>>> spacing
>>> AVLFG prng; ///< random
>>> char *tc_opt_string; ///< specified timecode option string
>>> AVRational tc_rate; ///< frame rate for timecode
>>> @@ -237,6 +240,7 @@ static const AVOption drawtext_options[]= {
>>> {"shadowcolor", "set shadow color", OFFSET(shadowcolor.rgba),
>>> AV_OPT_TYPE_COLOR, {.str="black"}, 0, 0, FLAGS},
>>> {"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},
>>> + {"letter_spacing", "set letter spacing in pixels",
>>> OFFSET(letter_spacing_expr), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS},
>>> {"line_spacing", "set line spacing in pixels",
>>> OFFSET(line_spacing), AV_OPT_TYPE_INT, {.i64=0}, INT_MIN,
>>> INT_MAX,FLAGS},
>>> {"fontsize", "set font size", OFFSET(fontsize_expr),
>>> AV_OPT_TYPE_STRING, {.str=NULL}, 0, 0 , FLAGS},
>>> {"x", "set x expression", OFFSET(x_expr),
>>> AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS},
>>> @@ -812,7 +816,7 @@ static av_cold int init(AVFilterContext *ctx)
>>> FT_STROKER_LINEJOIN_ROUND, 0);
>>> }
>>>
>>> - s->use_kerning = FT_HAS_KERNING(s->face);
>>> + s->use_kerning = FT_HAS_KERNING(s->face) && !s->letter_spacing;
>>>
>>> /* load the fallback glyph with code 0 */
>>> load_glyph(ctx, NULL, 0);
>>> @@ -857,8 +861,9 @@ static av_cold void uninit(AVFilterContext *ctx)
>>> av_expr_free(s->y_pexpr);
>>> av_expr_free(s->a_pexpr);
>>> av_expr_free(s->fontsize_pexpr);
>>> + av_expr_free(s->letter_spacing_pexpr);
>>>
>>> - s->x_pexpr = s->y_pexpr = s->a_pexpr = s->fontsize_pexpr = NULL;
>>> + s->x_pexpr = s->y_pexpr = s->a_pexpr = s->fontsize_pexpr =
>>> s->letter_spacing_pexpr = NULL;
>>>
>>> av_freep(&s->positions);
>>> s->nb_positions = 0;
>>> @@ -903,13 +908,16 @@ static int config_input(AVFilterLink *inlink)
>>> av_expr_free(s->x_pexpr);
>>> av_expr_free(s->y_pexpr);
>>> av_expr_free(s->a_pexpr);
>>> - s->x_pexpr = s->y_pexpr = s->a_pexpr = NULL;
>>> + av_expr_free(s->letter_spacing_pexpr);
>>> + s->x_pexpr = s->y_pexpr = s->a_pexpr = s->letter_spacing_pexpr =
>>> NULL;
>>>
>>> if ((ret = av_expr_parse(&s->x_pexpr, expr = s->x_expr, var_names,
>>> NULL, NULL, fun2_names, fun2, 0, ctx)) < 0
>>> ||
>>> (ret = av_expr_parse(&s->y_pexpr, expr = s->y_expr, var_names,
>>> NULL, NULL, fun2_names, fun2, 0, ctx)) < 0
>>> ||
>>> (ret = av_expr_parse(&s->a_pexpr, expr = s->a_expr, var_names,
>>> + NULL, NULL, fun2_names, fun2, 0, ctx)) < 0
>>> ||
>>> + (ret = av_expr_parse(&s->letter_spacing_pexpr, expr =
>>> s->letter_spacing_expr, var_names,
>>> NULL, NULL, fun2_names, fun2, 0, ctx)) < 0)
>>> {
>>> av_log(ctx, AV_LOG_ERROR, "Failed to parse expression: %s \n",
>>> expr);
>>> return AVERROR(EINVAL);
>>> @@ -1525,6 +1533,9 @@ continue_on_invalid2:
>>> dummy.fontsize = s->fontsize;
>>> glyph = av_tree_find(s->glyphs, &dummy, glyph_cmp, NULL);
>>>
>>> + /* letter spacing */
>>> + x += s->letter_spacing;
>>> +
>>> /* kerning */
>>> if (s->use_kerning && prev_glyph && glyph->code) {
>>> FT_Get_Kerning(s->face, prev_glyph->code, glyph->code,
>>> @@ -1539,7 +1550,12 @@ continue_on_invalid2:
>>> else x += glyph->advance;
>>> }
>>>
>>> - max_text_line_w = FFMAX(x, max_text_line_w);
>>> + s->letter_spacing = av_expr_eval(s->letter_spacing_pexpr,
>>> s->var_values, &s->prng);
>>> + if (s->letter_spacing < 0) {
>>> + max_text_line_w = x+ s->letter_spacing;
>>> + } else {
>>> + max_text_line_w = FFMAX(x, max_text_line_w) + s->letter_spacing;
>>> + }
>>>
>>> s->var_values[VAR_TW] = s->var_values[VAR_TEXT_W] = max_text_line_w;
>>> s->var_values[VAR_TH] = s->var_values[VAR_TEXT_H] = y +
>>> s->max_glyph_h;
>>> --
>>> 2.40.1
>>>
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