The BCC Linear Color Key filter creates a key based on the difference
between the color of each pixel and the specified Key Color. The color
comparison can be done in RGB or in HSL color space, and you can adjust the
relative importance of each RGB channel with the RGB Weights parameters.
BCC Linear Color Key also allows you to remove unwanted foreground objects or
restore opacity to a transparent region in the foreground using the Region of
Interest controls. This feature is useful when the foreground has an isolated
region that is similar in color to the background (for example, a person
wearing a tie of the same color as the background).