|Source image||Detail of source image||Detail of filtered image|
Because of the complexities of the algorithms, some BCC ﬁlters (for example, BCC Glow) can mix in color channels from pixels that were originally transparent. This creates a premultiplied alpha channel which includes transparency information in the color channels as well as in the alpha channel.The Premult ﬁlter sets the color channels of all transparent pixels to the selected color, giving the user control of the color that is mixed in these cases.
When you composite an image with a premultiplied alpha channel over a new background of a different color, the edges of the alpha channel show a “fringe” of the old background, because the edges of the alpha channel were blended with the original background color information. Premultiplied Alpha Key allows you to key out most of this unwanted color.
In the example below, the source image’s alpha channel was premultiplied with a blue background. When the B is composited over a new background, a blue fringe is visible in the semi-transparent pixels. The Premult ﬁlter removes the blue color from the edge pixels so that the white pixels blend smoothly with the red background.
Presets and Common Controls
BCC filters come with a library of factory installed presets plus the ability to create your own custom presets and preview them with the BCC FX Browser™.
BCC filters also include common controls that configure global effect preferences and other host-specific effect settings.
For more information about working with presets and other common controls, Click Here.
Premult With Color sets the color that will be removed.