[MPlayer-dev-eng] Re: [PATCH] New video filter: deblendlogo

[Zoltan Hidvegi]

Ivo wrote:
> Doing alpha deblending on chroma channels is utter nonsense. It only works 
> if the logo mask is all white, which means there is no chroma, so the 
> unblended chroma is preserved and only the luminance is corrected. With 
> colored logo's this won't work.

Why not?  RGB -> YUV is an affine tansformation, and affine
transformation of convex combination of points (i.e. alpha-bending) is
the convex combination of the affine transformed points.  This means
that alpha-bending works just fine in YUV, as long as you use the YUV
transformed logo image.

Zoli