[FFmpeg-cvslog] avfilter/vf_drawtext: implement text alignment
yethie
git at videolan.org
Mon Jun 19 23:41:40 EEST 2023
ffmpeg | branch: master | yethie <klimklim at tiscali.it> | Fri May 26 12:51:05 2023 +0200| [5f2d907de2ddefd024d161b66d63f8da6208d4d0] | committer: Paul B Mahol
avfilter/vf_drawtext: implement text alignment
Text can now be aligned vertically (top, middle, bottom) and horizontally (left, center, right)
relative to the background box.
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=5f2d907de2ddefd024d161b66d63f8da6208d4d0
---
doc/filters.texi | 6 ++++++
libavfilter/vf_drawtext.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 56 insertions(+), 1 deletion(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index da355eca64..891c051029 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -12384,6 +12384,12 @@ The default value of @var{boxcolor} is "white".
@item line_spacing
Set the line spacing in pixels. The default value of @var{line_spacing} is 0.
+ at item text_align
+Set the vertical and horizontal alignment of the text with respect to the box boundaries.
+The value must contain exactly two letters, one for the vertical alignment (T=top,
+M=middle, B=bottom) and one for the horizontal alignment (L=left, C=center, R=right).
+Please note that tab characters are only supported with the left horizontal alignment.
+
@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 417733596d..e147196844 100644
--- a/libavfilter/vf_drawtext.c
+++ b/libavfilter/vf_drawtext.c
@@ -309,12 +309,14 @@ typedef struct DrawTextContext {
int boxw; ///< the value of the boxw parameter
int boxh; ///< the value of the boxh parameter
+ uint8_t *text_align; ///< the horizontal and vertical text alignment
TextLine *lines; ///< computed information about text lines
int line_count; ///< the number of text lines
uint32_t *tab_clusters; ///< the position of tab characters in the text
int tab_count; ///< the number of tab characters
int blank_advance64; ///< the size of the space character
+ int tab_warning_printed; ///< ensure the tab warning to be printed only once
} DrawTextContext;
#define OFFSET(x) offsetof(DrawTextContext, x)
@@ -333,6 +335,7 @@ static const AVOption drawtext_options[]= {
{"boxborderw", "set box borders width", OFFSET(boxborderw), 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},
+ {"text_align", "set text alignment", OFFSET(text_align), AV_OPT_TYPE_STRING, {.str="TL"}, 0, 0, FLAGS},
{"x", "set x expression", OFFSET(x_expr), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS},
{"y", "set y expression", OFFSET(y_expr), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0, FLAGS},
{"boxw", "set box width", OFFSET(boxw), AV_OPT_TYPE_INT, {.i64=0}, 0, INT_MAX, FLAGS},
@@ -851,6 +854,19 @@ static int string_to_array(const char *source, int *result, int result_size)
return counter;
}
+static int validate_text_align(char* text_align)
+{
+ int err = 0;
+ if (strlen(text_align) != 2
+ || strchr("LCRTMB", text_align[0]) == NULL || strchr("LCRTMB", text_align[1]) == NULL
+ || (strchr("TMB", text_align[0]) != NULL && strchr("LCR", text_align[1]) == NULL)
+ || (strchr("LCR", text_align[0]) != NULL && strchr("TMB", text_align[1]) == NULL)) {
+ err = AVERROR(EINVAL);
+ }
+
+ return err;
+}
+
static av_cold int init(AVFilterContext *ctx)
{
int err;
@@ -916,6 +932,14 @@ static av_cold int init(AVFilterContext *ctx)
return AVERROR(EINVAL);
}
+ if ((err = validate_text_align(s->text_align))) {
+ av_log(ctx, AV_LOG_ERROR,
+ "The value provided for parameter 'text_align' is not valid,\n");
+ av_log(ctx, AV_LOG_ERROR,
+ "please specify a two characters string containing only one letter for horizontal alignment ('LCR') and one for vertical alignment ('TMB')\n");
+ return err;
+ }
+
#if CONFIG_LIBFRIBIDI
if (s->text_shaping)
if ((err = shape_text(ctx)) < 0)
@@ -1486,13 +1510,32 @@ static int draw_glyphs(DrawTextContext *s, AVFrame *frame,
Glyph dummy = { 0 }, *glyph;
FT_Bitmap bitmap;
FT_BitmapGlyph b_glyph;
+ uint8_t j_center = 0, j_right = 0, j_middle = 0, j_bottom = 0;
+ int line_w, offset_y = 0;
int clip_x = 0, clip_y = 0;
+ j_center = strstr(s->text_align, "C") > 0;
+ j_right = strstr(s->text_align, "R") > 0;
+ j_middle = strstr(s->text_align, "M") > 0;
+ j_bottom = strstr(s->text_align, "B") > 0;
+
+ if (j_middle) {
+ offset_y = (s->box_height - metrics->height) / 2;
+ } else if (j_bottom) {
+ offset_y = s->box_height - metrics->height;
+ }
+
+ if ((j_right || j_center) && !s->tab_warning_printed && s->tab_count > 0) {
+ s->tab_warning_printed = 1;
+ av_log(s, AV_LOG_WARNING, "Tab characters are only supported with left horizontal alignment\n");
+ }
+
clip_x = FFMIN(metrics->rect_x + s->box_width + s->bb_right, frame->width);
clip_y = FFMIN(metrics->rect_y + s->box_height + s->bb_bottom, frame->height);
for (l = 0; l < s->line_count; ++l) {
TextLine *line = &s->lines[l];
+ line_w = POS_CEIL(line->width64, 64);
for (g = 0; g < line->hb_data.glyph_count; ++g) {
info = &line->glyphs[g];
dummy.fontsize = s->fontsize;
@@ -1506,10 +1549,16 @@ static int draw_glyphs(DrawTextContext *s, AVFrame *frame,
b_glyph = borderw ? glyph->border_bglyph[idx] : glyph->bglyph[idx];
bitmap = b_glyph->bitmap;
x1 = x + info->x + b_glyph->left;
- y1 = y + info->y - b_glyph->top;
+ y1 = y + info->y - b_glyph->top + offset_y;
w1 = bitmap.width;
h1 = bitmap.rows;
+ if (j_center) {
+ x1 += (s->box_width - line_w) / 2;
+ } else if (j_right) {
+ x1 += s->box_width - line_w;
+ }
+
// Offset of the glyph's bitmap in the visible region
dx = dy = 0;
if (x1 < metrics->rect_x - s->bb_left) {
More information about the ffmpeg-cvslog
mailing list