User guide

139

Control (UI) Default Value Function

operation (continued) • ImageMin - min(F,B). This takes the minimum values of both

images.

• ImageMinus - B-F. This subtracts the foreground from the

background. For subtracting the background from the

foreground instead, see ImageFrom.

• ImageMultiply - FB. This multiplies the values of the

foreground by the values of the background. It can be used to

composite darker values from the foreground with the

background image - dark gray smoke shot against a white

background, for example.

• ImageOut - B(1-f). This only shows the areas of the

background that do not overlap with the alpha of the

foreground. This can be useful for combining mattes.

• ImageOver - F+B(1-f). This layers the foreground over the

background according to the alpha of the foreground. This is

the most commonly used operation. It's used when layering a

foreground element over a background plate.

• ImagePlus - F+B. This produces the sum of the foreground

and background. Note that the add algorithm may result in

pixel values higher than 1.0.

• ImageScreen - F+B-FB. This is similar to ImageHypot, but

clamps pixel values to 1.0. This is mostly useful for combining

mattes.

• ImageUnder - F(1-b)+B. This is the reverse of the ImageOver

operation. It layers the background over the foreground

according to the alpha of the background.

amount 1 Dissolves between the bg image at 0 and the full merge effect at

4 NODES I-K | IMAGEATOP