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drawtext: Add an alpha option

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And document both `draw` and `alpha`.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
pull/133/head
Luca Barbato 10 years ago
parent eaa2d123f0
commit 9b2c57bef5
2 changed files with 49 additions and 10 deletions
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  1. 11
      doc/filters.texi
  2. 48
      libavfilter/vf_drawtext.c

11
doc/filters.texi
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@ -1209,6 +1209,17 @@ The timestamp, expressed in seconds. It's NAN if the input timestamp is unknown.
The default value of @var{x} and @var{y} is 0.
@item draw
Draw the text only if the expression evaluates as non-zero.
The expression accepts the same variables @var{x, y} do.
The default value is 1.
@item alpha
Draw the text applying alpha blending. The value can
be either a number between 0.0 and 1.0
The expression accepts the same variables @var{x, y} do.
The default value is 1.
@item fontsize
The font size to be used for drawing text.
The default value of @var{fontsize} is 16.

48
libavfilter/vf_drawtext.c
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@ -152,6 +152,9 @@ typedef struct DrawTextContext {
char *d_expr;
AVExpr *d_pexpr;
int draw; ///< set to zero to prevent drawing
char *a_expr;
AVExpr *a_pexpr;
int alpha;
AVLFG prng; ///< random
} DrawTextContext;
@ -176,6 +179,7 @@ static const AVOption drawtext_options[]= {
{ "shadowy", NULL, OFFSET(shadowy), AV_OPT_TYPE_INT, { .i64 = 0 }, INT_MIN, INT_MAX, FLAGS },
{ "tabsize", NULL, OFFSET(tabsize), AV_OPT_TYPE_INT, { .i64 = 4 }, 0, INT_MAX, FLAGS },
{ "draw", "if false do not draw", OFFSET(d_expr), AV_OPT_TYPE_STRING, { .str = "1" }, .flags = FLAGS },
{ "alpha", "apply alpha while rendering", OFFSET(a_expr), AV_OPT_TYPE_STRING, { .str = "1" }, .flags = FLAGS },
{ "fix_bounds", "if true, check and fix text coords to avoid clipping",
OFFSET(fix_bounds), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, FLAGS },
@ -678,6 +682,8 @@ static int config_input(AVFilterLink *inlink)
(ret = av_expr_parse(&s->y_pexpr, s->y_expr, var_names,
NULL, NULL, fun2_names, fun2, 0, ctx)) < 0 ||
(ret = av_expr_parse(&s->d_pexpr, s->d_expr, var_names,
NULL, NULL, fun2_names, fun2, 0, ctx)) < 0 ||
(ret = av_expr_parse(&s->a_pexpr, s->a_expr, var_names,
NULL, NULL, fun2_names, fun2, 0, ctx)) < 0)
return AVERROR(EINVAL);
@ -713,7 +719,7 @@ static int config_input(AVFilterLink *inlink)
#define SET_PIXEL_YUV(frame, yuva_color, val, x, y, hsub, vsub) { \
luma_pos = ((x) ) + ((y) ) * frame->linesize[0]; \
alpha = yuva_color[3] * (val) * 129; \
alpha = yuva_color[3] * alpha_mul * (val) * 129 / 255; \
frame->data[0][luma_pos] = (alpha * yuva_color[0] + (255*255*129 - alpha) * frame->data[0][luma_pos] ) >> 23; \
if (((x) & ((1<<(hsub)) - 1)) == 0 && ((y) & ((1<<(vsub)) - 1)) == 0) {\
chroma_pos1 = ((x) >> (hsub)) + ((y) >> (vsub)) * frame->linesize[1]; \
@ -725,7 +731,8 @@ static int config_input(AVFilterLink *inlink)
static inline int draw_glyph_yuv(AVFrame *frame, FT_Bitmap *bitmap, unsigned int x,
unsigned int y, unsigned int width, unsigned int height,
const uint8_t yuva_color[4], int hsub, int vsub)
const uint8_t yuva_color[4], int hsub, int vsub,
int alpha_mul)
{
int r, c, alpha;
unsigned int luma_pos, chroma_pos1, chroma_pos2;
@ -747,7 +754,7 @@ static inline int draw_glyph_yuv(AVFrame *frame, FT_Bitmap *bitmap, unsigned int
#define SET_PIXEL_RGB(frame, rgba_color, val, x, y, pixel_step, r_off, g_off, b_off, a_off) { \
p = frame->data[0] + (x) * pixel_step + ((y) * frame->linesize[0]); \
alpha = rgba_color[3] * (val) * 129; \
alpha = rgba_color[3] * alpha_mul * (val) * 129 / 255; \
*(p+r_off) = (alpha * rgba_color[0] + (255*255*129 - alpha) * *(p+r_off)) >> 23; \
*(p+g_off) = (alpha * rgba_color[1] + (255*255*129 - alpha) * *(p+g_off)) >> 23; \
*(p+b_off) = (alpha * rgba_color[2] + (255*255*129 - alpha) * *(p+b_off)) >> 23; \
@ -756,7 +763,8 @@ static inline int draw_glyph_yuv(AVFrame *frame, FT_Bitmap *bitmap, unsigned int
static inline int draw_glyph_rgb(AVFrame *frame, FT_Bitmap *bitmap,
unsigned int x, unsigned int y,
unsigned int width, unsigned int height, int pixel_step,
const uint8_t rgba_color[4], const uint8_t rgba_map[4])
const uint8_t rgba_color[4], const uint8_t rgba_map[4],
int alpha_mul)
{
int r, c, alpha;
uint8_t *p;
@ -780,11 +788,12 @@ static inline int draw_glyph_rgb(AVFrame *frame, FT_Bitmap *bitmap,
static inline void drawbox(AVFrame *frame, unsigned int x, unsigned int y,
unsigned int width, unsigned int height,
uint8_t *line[4], int pixel_step[4], uint8_t color[4],
int hsub, int vsub, int is_rgba_packed, uint8_t rgba_map[4])
int hsub, int vsub, int is_rgba_packed, uint8_t rgba_map[4],
int alpha_mul)
{
int i, j, alpha;
if (color[3] != 0xFF) {
if (color[3] != 0xFF || alpha_mul != 0xFF) {
if (is_rgba_packed) {
uint8_t *p;
for (j = 0; j < height; j++)
@ -805,7 +814,9 @@ static inline void drawbox(AVFrame *frame, unsigned int x, unsigned int y,
}
static int draw_glyphs(DrawTextContext *s, AVFrame *frame,
int width, int height, const uint8_t rgbcolor[4], const uint8_t yuvcolor[4], int x, int y)
int width, int height,
const uint8_t rgbcolor[4], const uint8_t yuvcolor[4],
int x, int y)
{
char *text = HAVE_LOCALTIME_R ? s->expanded_text : s->text;
uint32_t code = 0;
@ -831,11 +842,11 @@ static int draw_glyphs(DrawTextContext *s, AVFrame *frame,
if (s->is_packed_rgb) {
draw_glyph_rgb(frame, &glyph->bitmap,
s->positions[i].x+x, s->positions[i].y+y, width, height,
s->pixel_step[0], rgbcolor, s->rgba_map);
s->pixel_step[0], rgbcolor, s->rgba_map, s->alpha);
} else {
draw_glyph_yuv(frame, &glyph->bitmap,
s->positions[i].x+x, s->positions[i].y+y, width, height,
yuvcolor, s->hsub, s->vsub);
yuvcolor, s->hsub, s->vsub, s->alpha);
}
}
@ -853,7 +864,7 @@ static int draw_text(AVFilterContext *ctx, AVFrame *frame,
drawbox(frame, s->x, s->y, s->w, s->h,
s->box_line, s->pixel_step, s->boxcolor,
s->hsub, s->vsub, s->is_packed_rgb,
s->rgba_map);
s->rgba_map, s->alpha);
if (s->shadowx || s->shadowy) {
if ((ret = draw_glyphs(s, frame, width, height,
@ -889,6 +900,21 @@ static inline int normalize_double(int *n, double d)
return ret;
}
static void update_alpha(DrawTextContext *s)
{
double alpha = av_expr_eval(s->a_pexpr, s->var_values, &s->prng);
if (isnan(alpha))
return;
if (alpha >= 1.0)
s->alpha = 255;
else if (alpha <= 0)
s->alpha = 0;
else
s->alpha = 256 * alpha;
}
static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
{
AVFilterContext *ctx = inlink->dst;
@ -912,6 +938,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
s->draw = av_expr_eval(s->d_pexpr, s->var_values, &s->prng);
update_alpha(s);
normalize_double(&s->x, s->var_values[VAR_X]);
normalize_double(&s->y, s->var_values[VAR_Y]);

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