[FFmpeg-devel] [PATCH] swscale alpha channel support

[Øyvind Kolås]

On Sun, Mar 22, 2009 at 6:01 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> and doing what you suggest will cause artifacts in other cases, like for
> example if i take the famous lena image and make her eyes 100% transparent
> and then rescale and afterwards make them non transparent

This is correct I'd expect such a matte / mask video to be a separate
grayscale sequence of frames if it is expected to be edited.

> the only real problem i see with the current code is that pixels that
> have undefined color and 100% transparency could bleed into non transparent
> areas. Thats something that could be fixed by a pre-pass.

This pre-pass surely is something that is going to be as expensive as
the pre-multiplication and
I think it is a rather non-standard thing to do.

/?yvind K.

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