[FFmpeg-devel] [PATCH] imgconvert: add macro pixdesc_has_alpha for checking if a pixel format has an alpha component

[Stefano Sabatini]

On date Thursday 2012-03-08 17:01:28 +0100, Michael Niedermayer encoded:
> On Thu, Mar 08, 2012 at 02:44:47PM +0100, Stefano Sabatini wrote:
> > Reduce redundancy and simplify.
> > ---
> >  libavcodec/imgconvert.c |   21 ++++++---------------
> >  1 files changed, 6 insertions(+), 15 deletions(-)
> > 
> > diff --git a/libavcodec/imgconvert.c b/libavcodec/imgconvert.c
> > index 058a0d5..0d1ce3f 100644
> > --- a/libavcodec/imgconvert.c
> > +++ b/libavcodec/imgconvert.c
> > @@ -55,9 +55,12 @@
> >  #define deinterlace_line         deinterlace_line_c
> >  #endif
> >  
> > +#define pixdesc_has_alpha(pix_desc)                                     \
> > +    (pix_desc->nb_components == 2 || pix_desc->nb_components == 4       \
> > +     || pix_desc->flags & PIX_FMT_PAL)
> 
> does this match is_alpha for all pix fmts ?

These are the alpha formats, after and before:
pal8
argb
rgba
abgr
bgra
yuva420p
gray8a
rgba64be
rgba64le
bgra64be
bgra64le
yuva444p

Note that this is the same trick employed in libswscale.
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