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lavfi/overlay: enable yuva420p as overlay background

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Same calculation as for RGBA etc to create unpremultiplied output.
Useful for creating an intermediate "Mix/Effects bank", in vision mixer
(switcher) terminology.

Example command:

ffmpeg -i input.mov -vf
"[in]scale=iw:ih:interl=1,format=yuv420p[bg];movie=BBC_blocks_watermark.png,scale=iw:ih:interl=1,format=yuva420p[dog];movie=Kickabout_strap.mov,scale=iw:ih:interl=1,format=yuva420p[strap];[strap][dog]overlay=0:0[me1];[bg][me1]overlay=0:0,scale=0:0:interl=1[out]"
-b:v 3M -an output.mov

Fix trac ticket #549.

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
This commit is contained in:
Mark Himsley 2012-11-25 15:24:29 +00:00 committed by Stefano Sabatini
parent 8aa6d899c0
commit 13c6252536
2 changed files with 61 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
libavfilter/version.h
View File

@ -30,7 +30,7 @@
#define LIBAVFILTER_VERSION_MAJOR 3
#define LIBAVFILTER_VERSION_MINOR 23
#define LIBAVFILTER_VERSION_MICRO 102
#define LIBAVFILTER_VERSION_MICRO 103
#define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
LIBAVFILTER_VERSION_MINOR, \

70
libavfilter/vf_overlay.c
View File

@ -157,7 +157,7 @@ static int query_formats(AVFilterContext *ctx)
OverlayContext *over = ctx->priv;
/* overlay formats contains alpha, for avoiding conversion with alpha information loss */
const enum AVPixelFormat main_pix_fmts_yuv[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };
const enum AVPixelFormat main_pix_fmts_yuv[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUVA420P, AV_PIX_FMT_NONE };
const enum AVPixelFormat overlay_pix_fmts_yuv[] = { AV_PIX_FMT_YUVA420P, AV_PIX_FMT_NONE };
const enum AVPixelFormat main_pix_fmts_rgb[] = {
AV_PIX_FMT_ARGB, AV_PIX_FMT_RGBA,
@ -293,6 +293,12 @@ static AVFilterBufferRef *get_video_buffer(AVFilterLink *link, int perms, int w,
// apply a fast variant: (X+127)/255 = ((X+127)*257+257)>>16 = ((X+128)*257)>>16
#define FAST_DIV255(x) ((((x) + 128) * 257) >> 16)
// calculate the unpremultiplied alpha, applying the general equation:
// alpha = alpha_overlay / ( (alpha_main + alpha_overlay) - (alpha_main * alpha_overlay) )
// (((x) << 16) - ((x) << 9) + (x)) is a faster version of: 255 * 255 * x
// ((((x) + (y)) << 8) - ((x) + (y)) - (y) * (x)) is a faster version of: 255 * (x + y)
#define UNPREMULTIPLY_ALPHA(x, y) ((((x) << 16) - ((x) << 9) + (x)) / ((((x) + (y)) << 8) - ((x) + (y)) - (y) * (x)))
static void blend_slice(AVFilterContext *ctx,
AVFilterBufferRef *dst, AVFilterBufferRef *src,
int x, int y, int w, int h,
@ -336,15 +342,8 @@ static void blend_slice(AVFilterContext *ctx,
// if the main channel has an alpha channel, alpha has to be calculated
// to create an un-premultiplied (straight) alpha value
if (main_has_alpha && alpha != 0 && alpha != 255) {
// apply the general equation:
// alpha = alpha_overlay / ( (alpha_main + alpha_overlay) - (alpha_main * alpha_overlay) )
alpha =
// the next line is a faster version of: 255 * 255 * alpha
( (alpha << 16) - (alpha << 9) + alpha )
/
// the next line is a faster version of: 255 * (alpha + d[da])
( ((alpha + d[da]) << 8 ) - (alpha + d[da])
- d[da] * alpha );
uint8_t alpha_d = d[da];
alpha = UNPREMULTIPLY_ALPHA(alpha, alpha_d);
}
switch (alpha) {
@ -381,6 +380,39 @@ static void blend_slice(AVFilterContext *ctx,
sp += src->linesize[0];
}
} else {
const int main_has_alpha = over->main_has_alpha;
if (main_has_alpha) {
uint8_t *da = dst->data[3] + x * over->main_pix_step[3] +
start_y * dst->linesize[3];
uint8_t *sa = src->data[3];
uint8_t alpha; ///< the amount of overlay to blend on to main
if (slice_y > y)
sa += (slice_y - y) * src->linesize[3];
for (i = 0; i < height; i++) {
uint8_t *d = da, *s = sa;
for (j = 0; j < width; j++) {
alpha = *s;
if (alpha != 0 && alpha != 255) {
uint8_t alpha_d = *d;
alpha = UNPREMULTIPLY_ALPHA(alpha, alpha_d);
}
switch (alpha) {
case 0:
break;
case 255:
*d = *s;
break;
default:
// apply alpha compositing: main_alpha += (1-main_alpha) * overlay_alpha
*d += FAST_DIV255((255 - *d) * *s);
}
d += 1;
s += 1;
}
da += dst->linesize[3];
sa += src->linesize[3];
}
}
for (i = 0; i < 3; i++) {
int hsub = i ? over->hsub : 0;
int vsub = i ? over->vsub : 0;
@ -410,6 +442,24 @@ static void blend_slice(AVFilterContext *ctx,
alpha = (alpha_v + alpha_h) >> 1;
} else
alpha = a[0];
// if the main channel has an alpha channel, alpha has to be calculated
// to create an un-premultiplied (straight) alpha value
if (main_has_alpha && alpha != 0 && alpha != 255) {
// average alpha for color components, improve quality
uint8_t alpha_d;
if (hsub && vsub && j+1 < hp && k+1 < wp) {
alpha_d = (d[0] + d[src->linesize[3]] +
d[1] + d[src->linesize[3]+1]) >> 2;
} else if (hsub || vsub) {
alpha_h = hsub && k+1 < wp ?
(d[0] + d[1]) >> 1 : d[0];
alpha_v = vsub && j+1 < hp ?
(d[0] + d[src->linesize[3]]) >> 1 : d[0];
alpha_d = (alpha_v + alpha_h) >> 1;
} else
alpha_d = d[0];
alpha = UNPREMULTIPLY_ALPHA(alpha, alpha_d);
}
*d = FAST_DIV255(*d * (255 - alpha) + *s * alpha);
s++;
d++;