I attach the new image of the overlays to replace "normal.png" in the manual. It seems to me that the original image corresponding to "Subtract" is wrong: it corresponds to the Porter-Duff type overlay called "SrcOut". The test I did using the green and red of the original image seems to me to lead to a correct result.
Green (ColorPicker): R = 0.1020 G = 0.8078 B = 0.2980 Red (ColorPicker): R = 0.7333 G = 0.1686 B = 0.2980 Subtract: Alpha Chroma (Sa - Da); (Sc - Dc) (0 - 0); ([0.1020-0.7333], [0.8078-0.1686], [0.2980-02980]) 0 ; (0, 0.6392, 0) The ColorPicker indicates that the green resulting from "Subtract" is exactly (0, 0.6392, 0) I don't really understand this whole overlays thing, especially if they have to do with plugins that use the alpha channel (Reroute and Invert Video, for example). I hope IgorBeg can say something, because he has gone into this topic a lot. Andrew's proposal to add in the pulldown a new section with CinCV overlays sounds great to me because if we can't reproduce the results of the tutorial, something must be wrong. Even just the fact that we cannot use YUVA, but only RGBA. PS: the definition of "Subtract" given in the manual seems to me to match the definition on the "rippletraining" website that you posted. I would not modify it...
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