Blurs the alpha channel of an image, performs levels and gamma correction on the output of the blur, and composites the output alpha with the initial alpha using the chosen apply mode.
Used for compositing camera footage shot using a blue, green, or red screen as a backdrop over a new background video or a still image from a separate file.
Contracts or expands the edges of the matte to bring them closer to or
farther from the foreground. Two Choke controls allow you to smoothly adjust the matte.
