[FFmpeg-devel] [PATCH 6/6] avcodec/apng: Add partial support for blending with PAL8 pixel format

[Michael Niedermayer]

On Tue, Jun 02, 2015 at 03:49:27PM +0000, Donny Yang wrote:
> Currently restricted to blending pixels that only contain either
> 0 or 255 in their alpha components
> 
> Signed-off-by: Donny Yang <work at kota.moe>
> ---
>  libavcodec/pngdec.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
> index 1667530..4063347 100644
> --- a/libavcodec/pngdec.c
> +++ b/libavcodec/pngdec.c
> @@ -892,7 +892,8 @@ static int handle_p_frame_apng(AVCodecContext *avctx, PNGDecContext *s,
>  
>      if (s->blend_op == APNG_BLEND_OP_OVER &&
>          avctx->pix_fmt != AV_PIX_FMT_RGBA &&
> -        avctx->pix_fmt != AV_PIX_FMT_GRAY8A) {
> +        avctx->pix_fmt != AV_PIX_FMT_GRAY8A &&
> +        avctx->pix_fmt != AV_PIX_FMT_PAL8) {
>          avpriv_request_sample(avctx, "Blending with pixel format %s",
>                                av_get_pix_fmt_name(avctx->pix_fmt));
>          return AVERROR_PATCHWELCOME;
> @@ -941,6 +942,11 @@ static int handle_p_frame_apng(AVCodecContext *avctx, PNGDecContext *s,
>                      foreground_alpha = foreground[1];
>                      background_alpha = background[1];
>                      break;
> +
> +                case AV_PIX_FMT_PAL8:
> +                    foreground_alpha = s->palette[foreground[0]] >> 24;
> +                    background_alpha = s->palette[background[0]] >> 24;
> +                    break;
>                  }
>  
>                  if (foreground_alpha == 0)
> @@ -951,6 +957,13 @@ static int handle_p_frame_apng(AVCodecContext *avctx, PNGDecContext *s,
>                      continue;
>                  }
>  
> +                if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {

> +                    // TODO: Alpha blending with PAL8 will likely need the entire image converted over to RGBA first

yes, thats what i suspect as well

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
people will find a way around the laws. -- Plato
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