Alpha Operations

The Alpha Operations composition types require an alpha channel in the clips on the blend and base track. If the clips do not have an alpha channel, you can add one by using effects from the Alpha, masque et incrustation effects category.

Changing the composition type Alpha operation

You can change the Alpha Operation by selecting from the Composition Type drop-down list.

For this comparison, title clips were used for the orange square on the blend track, and for a blue circle in the base track.

Composition Type	Example	Notes
Default composite		The square on the upper track (blend track) covers part of the circle on the lower track (base track)
Alpha ATOP		Draw a pixel from the base layer on top of the blend layer if both layers have a non-alpha pixel (frei0r.alphaatop)
Alpha IN		Draw a pixel from the base layer only where both layers have a non-alpha pixel. This is the alpha equivalent of clipping. (frei0r.alphain)
Alpha OUT		Draw an alpha pixel only where both layers have a non-alpha pixel, otherwise draw the pixel from the base layer. This is the alpha equivalent of clipping. (frei0r.alphaout)
Alpha OVER		Overlay the blend layer with the base layer (frei0r.alphaover)
Alpha XOR		Draw a pixel only where either layer has a pixel, and no pixel (alpha) where both layers have a pixel (frei0r.alphaxor)