User guide

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Control (UI) Default Value Function
operation (continued) • ImageIn - Bf. This only shows the areas of the background
that overlap with the alpha of the foreground. It can be useful
for combining mattes.
• ImageMatte - Ff*B(1-f). This is a premultiplied ImageOver.
Use unpremultiplied images with this operation.
• ImageMax - max(F,B). This takes the maximum values of both
images. This is a good way to combine mattes and useful for
bringing aspects like bright hair detail through.
• 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
1.
4 NODES I-K | IMAGEMULTIPLY