[FFmpeg-devel] [PATCH] avfilter/drawutils: allow drawing opaque text on transparent background

[Michael Niedermayer]

On Wed, Sep 14, 2016 at 01:38:20AM +0200, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
> Fixes #3302.
> ---
>  libavfilter/drawutils.c   | 7 ++++---
>  libavfilter/drawutils.h   | 1 +
>  libavfilter/vf_drawtext.c | 2 +-
>  3 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/libavfilter/drawutils.c b/libavfilter/drawutils.c
> index f6760be..905eaa3 100644
> --- a/libavfilter/drawutils.c
> +++ b/libavfilter/drawutils.c
> @@ -211,10 +211,11 @@ int ff_draw_init(FFDrawContext *draw, enum AVPixelFormat format, unsigned flags)
>      draw->desc      = desc;
>      draw->format    = format;
>      draw->nb_planes = nb_planes;
> +    draw->flags     = flags;
>      memcpy(draw->pixelstep, pixelstep, sizeof(draw->pixelstep));
>      draw->hsub[1] = draw->hsub[2] = draw->hsub_max = desc->log2_chroma_w;
>      draw->vsub[1] = draw->vsub[2] = draw->vsub_max = desc->log2_chroma_h;
> -    for (i = 0; i < (desc->nb_components - !!(desc->flags & AV_PIX_FMT_FLAG_ALPHA)); i++)
> +    for (i = 0; i < (desc->nb_components - !!(desc->flags & AV_PIX_FMT_FLAG_ALPHA && !(flags & 1))); i++)
>          draw->comp_mask[desc->comp[i].plane] |=
>              1 << desc->comp[i].offset;
>      return 0;
> @@ -452,7 +453,7 @@ void ff_blend_rectangle(FFDrawContext *draw, FFDrawColor *color,
>          /* 0x101 * alpha is in the [ 2 ; 0x1001] range */
>          alpha = 0x101 * color->rgba[3] + 0x2;
>      }
> -    nb_planes = draw->nb_planes - !!(draw->desc->flags & AV_PIX_FMT_FLAG_ALPHA);
> +    nb_planes = draw->nb_planes - !!(draw->desc->flags & AV_PIX_FMT_FLAG_ALPHA && !(draw->flags & 1));
>      nb_planes += !nb_planes;
>      for (plane = 0; plane < nb_planes; plane++) {
>          nb_comp = draw->pixelstep[plane];
> @@ -630,7 +631,7 @@ void ff_blend_mask(FFDrawContext *draw, FFDrawColor *color,
>      } else {
>          alpha = (0x101 * color->rgba[3] + 0x2) >> 8;
>      }
> -    nb_planes = draw->nb_planes - !!(draw->desc->flags & AV_PIX_FMT_FLAG_ALPHA);
> +    nb_planes = draw->nb_planes - !!(draw->desc->flags & AV_PIX_FMT_FLAG_ALPHA && !(draw->flags & 1));
>      nb_planes += !nb_planes;
>      for (plane = 0; plane < nb_planes; plane++) {
>          nb_comp = draw->pixelstep[plane];
> diff --git a/libavfilter/drawutils.h b/libavfilter/drawutils.h
> index 1fb3e4f..11ec97a 100644
> --- a/libavfilter/drawutils.h
> +++ b/libavfilter/drawutils.h
> @@ -55,6 +55,7 @@ typedef struct FFDrawContext {
>      uint8_t vsub[MAX_PLANES];  /*< vertical subsampling */
>      uint8_t hsub_max;
>      uint8_t vsub_max;
> +    unsigned flags;
>  } FFDrawContext;
>  
>  typedef struct FFDrawColor {
> diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
> index 214aef0..996c26d 100644
> --- a/libavfilter/vf_drawtext.c
> +++ b/libavfilter/vf_drawtext.c
> @@ -730,7 +730,7 @@ static int config_input(AVFilterLink *inlink)
>      DrawTextContext *s = ctx->priv;
>      int ret;
>  
> -    ff_draw_init(&s->dc, inlink->format, 0);
> +    ff_draw_init(&s->dc, inlink->format, 1);

the docs need an update they say "No flags currently defined."
also a named identifer would be more descriptive than 1


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Never trust a computer, one day, it may think you are the virus. -- Compn
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