by Gepetto » Wed Sep 06, 2006 5:07 pm
CHANNELS IN AN RGBA IMAGE:
Red: Stores information for the amount of red in each pixel.
Green: Stores information for the amount of green in each pixel.
Blue: Stores information for the amount of blue in each pixel.
Alpha: : Stores information for the opacity in each pixel.
Video editors that handle alpha treat every video file that does not come with an alpha channel as if it had a full-opaque alpha channel, and you can edit that. Image editors usually have an "add alpha" function, just look for it.
Also, it's unlikely that you've "seen" videos with alpha channels because no one distributes video in RGBA colorspace. It's a waste of kilobytes.
About EDITING/CHANGING/ALTERING the alpha channel, there's about a quarter million ways to do that, so you'd have to say what exactly you're going for.
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