[FFmpeg-cvslog] drawtext: Add an alpha option
Luca Barbato
git at videolan.org
Tue Apr 21 20:28:06 CEST 2015
ffmpeg | branch: master | Luca Barbato <lu_zero at gentoo.org> | Sat Apr 11 19:04:25 2015 +0200| [9b2c57bef5e2f3f61a5fd708ba7d5351f5b3f386] | committer: Luca Barbato
drawtext: Add an alpha option
And document both `draw` and `alpha`.
Signed-off-by: Luca Barbato <lu_zero at gentoo.org>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=9b2c57bef5e2f3f61a5fd708ba7d5351f5b3f386
---
doc/filters.texi | 11 +++++++++++
libavfilter/vf_drawtext.c | 48 +++++++++++++++++++++++++++++++++++----------
2 files changed, 49 insertions(+), 10 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index 28e3292..e36f9a2 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -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.
+ at 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.
+
+ at 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.
diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
index 82e805b..97d44c6 100644
--- a/libavfilter/vf_drawtext.c
+++ b/libavfilter/vf_drawtext.c
@@ -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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