[FFmpeg-devel] [PATCH] swscale: Implement alphablendaway for planar 4:4:4 formats

[Ronald S. Bultje]

Hi,

On Fri, Aug 7, 2015 at 6:43 AM, Michael Niedermayer <michael at niedermayer.cc>
wrote:

> On Thu, Aug 06, 2015 at 10:24:52PM -0400, Ronald S. Bultje wrote:
> > Hi,
> >
> > On Thu, Aug 6, 2015 at 4:27 PM, Michael Niedermayer <michaelni at gmx.at>
> > wrote:
> >
> > > From: Michael Niedermayer <michael at niedermayer.cc>
> > >
> > > Fixes Ticket4746
> > >
> > > TODO: implement packed formats and subsampled formats
> > >
> > > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > > ---
> > >  doc/scaler.texi               |   13 ++++++
> > >  libswscale/Makefile           |    3 +-
> > >  libswscale/alphablend.c       |   55 +++++++++++++++++++++++
> > >  libswscale/options.c          |    3 ++
> > >  libswscale/swscale_internal.h |   12 +++++
> > >  libswscale/utils.c            |   97
> > > +++++++++++++++++++++++++++++++++++++++++
> > >  6 files changed, 182 insertions(+), 1 deletion(-)
> > >  create mode 100644 libswscale/alphablend.c
> > >
> > > diff --git a/doc/scaler.texi b/doc/scaler.texi
> > > index 23d6393..4c55334 100644
> > > --- a/doc/scaler.texi
> > > +++ b/doc/scaler.texi
> > > @@ -122,6 +122,19 @@ a_dither).
> > >
> > >  @end table
> > >
> > > + at item alphablend
> > > +Set the alpha blending to use when the input has alpha but the output
> > > does not.
> > > +Default value is @samp{black}.
> > > +
> > > + at table @samp
> > > + at item black
> > > +Blend onto black
> > > +
> > > + at item none
> > > +No blending
> > > +
> > > + at end table
> > > +
> > >  @end table
> >
> >
> > I must admit I'm not a fan of having just two values for something like
> > this. It seems to me you want 2 options, "blendmode", being "none" or
> > "background" (or a float/alpha between 1.0/0.0), and the actual
> background
> > color (black, white, blue, r=a,g=b,c=d). "black" vs. "none" seems like a
> > future compat nightmare. Is it that hard to implement a proper rgb/yuv
> > value solution?
>
> The color value convertion support is in drawutils which is in
> libavfilter. also drawutils lacks support for >8bit formats
> so to get arbitrary color support with a clean non duplicated
> implementation it would require moving drawutils
> or the color related code from it to libavutil and extending it to
> support all pixel formats. Unless iam missing something
>
> Also i wanted to implement support for a checkerboard background
> (which some applications use as default and it shows what
> is transparent much better than black would)
>
> So i would suggest that we implement ATM a "none" + "solidcolor" or
> "background" or what name is preferred
> and ill add a black/white checkerboard mode later and once drawutils
> exist in libavutil we can then easily add a "blendcolor" AVOption
> to specify the exact color
>
> If noone objects then ill work on that (except drawutils moving and
> extending)


Sounds ok.

Ronald