Re: [FFmpeg-devel] [PATCH] Revert "avfilter/vf_palette(gen|use): support palettes with alpha"

From: Soft Works <softworkz@hotmail.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Cc: "Clément Bœsch" <u@pkh.me>
Subject: Re: [FFmpeg-devel] [PATCH] Revert "avfilter/vf_palette(gen|use): support palettes with alpha"
Date: Sun, 30 Oct 2022 22:55:31 +0000
Message-ID: <DM8P223MB03652D145FF34A6D9A6FC527BA349@DM8P223MB0365.NAMP223.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <DM8P223MB03653424D89B55C2D3720173BA349@DM8P223MB0365.NAMP223.PROD.OUTLOOK.COM>

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of
> Soft Works
> Sent: Sunday, October 30, 2022 10:41 PM
> To: FFmpeg development discussions and patches <ffmpeg-
> devel@ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH] Revert
> "avfilter/vf_palette(gen|use): support palettes with alpha"
> 
> 
> 
> > -----Original Message-----
> > From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of
> > Clément Bœsch
> > Sent: Sunday, October 30, 2022 10:30 PM
> > To: FFmpeg development discussions and patches <ffmpeg-
> > devel@ffmpeg.org>
> > Subject: Re: [FFmpeg-devel] [PATCH] Revert
> > "avfilter/vf_palette(gen|use): support palettes with alpha"
> >
> > On Sun, Oct 30, 2022 at 09:19:05PM +0000, Soft Works wrote:
> > [...]
> > > At the time of submission I did a lot of experiments and the
> > results
> > > seemed to be very useful:
> > >
> > >
> https://gist.github.com/softworkz/deef5c2a43d3d629c3e17f9e21544a8f
> > >
> >
> > On that page, the result of the command using palette* filters for
> > the
> > colored "O" gives a broken output, and it's not a simple bug, it's
> > more
> > fundamental. You cannot just just average the colors with different
> > levels
> > of alpha, it makes no sense.
> >
> > Do you understand why or do you need me to elaborate?
> 
> I understand why. I know that it's not perfect. But it's the best
> what's achievable within the way the filter is working.
> 
> But I wouldn't go that far as saying it would be "broken". I think
> the result is quite acceptable with regards to the method being
> using.
> 
> The patch I had submitted doesn't change the previous behavior
> without the use_alpha parameter.
> And when using the use_alpha parameter, the results are still
> useful in many cases - maybe not always.
> 
> But it don't see any reason to remove this just because it's not
> perfect. If you would have a patch to improve the results - that
> would be a different story and of course very welcome.

I'm really not an expert in image processing algorithms, and I 
haven't tried the following yet:
Do you think it might make sense to put more weight on the 
alpha value by tripling it? So it would be weighted equally to the 
RGB value?

softworkz

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