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avfilter/vf_drawtext: add expression variables to control font ascent/descent

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The following new variables can be used in the x and y expressions: font_a, font_d, top_a, bottom_d.
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yethie 2023-05-26 12:46:10 +02:00 committed by Paul B Mahol
parent fac7bb06d8
commit 01d843f6d0
2 changed files with 24 additions and 0 deletions
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12
doc/filters.texi
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@ -12597,6 +12597,18 @@ contained in the rendered text, it is equivalent to @var{ascent} -
maximum glyph width, that is the maximum width for all the glyphs maximum glyph width, that is the maximum width for all the glyphs
contained in the rendered text contained in the rendered text
@item font_a
the ascent size defined in the font metrics
@item font_d
the descent size defined in the font metrics
@item top_a
the maximum ascender of the glyphs of the first text line
@item bottom_d
the maximum descender of the glyphs of the last text line
@item n @item n
the number of input frame, starting from 0 the number of input frame, starting from 0

12
libavfilter/vf_drawtext.c
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@ -89,6 +89,10 @@ static const char *const var_names[] = {
"max_glyph_d", "descent", ///< min glyph descender "max_glyph_d", "descent", ///< min glyph descender
"max_glyph_h", ///< max glyph height "max_glyph_h", ///< max glyph height
"max_glyph_w", ///< max glyph width "max_glyph_w", ///< max glyph width
"font_a", ///< font-defined ascent
"font_d", ///< font-defined descent
"top_a", ///< max glyph ascender of the top line
"bottom_d", ///< max glyph descender of the bottom line
"n", ///< number of frame "n", ///< number of frame
"sar", "sar",
"t", ///< timestamp expressed in seconds "t", ///< timestamp expressed in seconds
@ -136,6 +140,10 @@ enum var_name {
VAR_MAX_GLYPH_D, VAR_DESCENT, VAR_MAX_GLYPH_D, VAR_DESCENT,
VAR_MAX_GLYPH_H, VAR_MAX_GLYPH_H,
VAR_MAX_GLYPH_W, VAR_MAX_GLYPH_W,
VAR_FONT_A,
VAR_FONT_D,
VAR_TOP_A,
VAR_BOTTOM_D,
VAR_N, VAR_N,
VAR_SAR, VAR_SAR,
VAR_T, VAR_T,
@ -1800,8 +1808,12 @@ static int draw_text(AVFilterContext *ctx, AVFrame *frame)
s->var_values[VAR_MAX_GLYPH_W] = s->max_glyph_w; s->var_values[VAR_MAX_GLYPH_W] = s->max_glyph_w;
s->var_values[VAR_MAX_GLYPH_H] = s->max_glyph_h; s->var_values[VAR_MAX_GLYPH_H] = s->max_glyph_h;
s->var_values[VAR_MAX_GLYPH_A] = s->var_values[VAR_ASCENT] = POS_CEIL(metrics.max_y64, 64); s->var_values[VAR_MAX_GLYPH_A] = s->var_values[VAR_ASCENT] = POS_CEIL(metrics.max_y64, 64);
s->var_values[VAR_FONT_A] = s->face->size->metrics.ascender / 64;
s->var_values[VAR_MAX_GLYPH_D] = s->var_values[VAR_DESCENT] = POS_CEIL(metrics.min_y64, 64); s->var_values[VAR_MAX_GLYPH_D] = s->var_values[VAR_DESCENT] = POS_CEIL(metrics.min_y64, 64);
s->var_values[VAR_FONT_D] = -s->face->size->metrics.descender / 64;
s->var_values[VAR_TOP_A] = POS_CEIL(metrics.offset_top64, 64);
s->var_values[VAR_BOTTOM_D] = -POS_CEIL(metrics.offset_bottom64, 64);
s->var_values[VAR_LINE_H] = s->var_values[VAR_LH] = metrics.line_height64 / 64.; s->var_values[VAR_LINE_H] = s->var_values[VAR_LH] = metrics.line_height64 / 64.;
if (s->text_source == AV_FRAME_DATA_DETECTION_BBOXES) { if (s->text_source == AV_FRAME_DATA_DETECTION_BBOXES) {