Premultiply Tool

Premultiplication is the process where an image's RGB channels are multiplied by its alpha channel. Composite nodes expect unpremultiplied images. Furthermore, if you plan to use color correction, the images must be unpremultiplied.

The Premultiply tool lets you take an input image and create an image where each pixel’s color component is multiplied by the pixel's alpha component. The multiplication result is clamped to the color range of the output image.

To premultiply an image using the Premultiply tool:

1. Drag the Premultiply tool from the Formatting folder into the dependency graph in the Schematic view.
   

   The image is premultiplied.

   NoteWhen using the Premultiply tool, make sure the output image is never processed by a tool that produces incorrect results while operating on an image with premultiplied data. Tracking of whether images are stored in premultiplied format or not, does not occur.

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