Hi there, I'm relatively new to Actionscript, and for a particular image operation I need to be able to fill *just* the alpha channel of a bitmapData object with a shape, without destroying the color data. Basically, I've got a bitmapData object with a bitmap loaded into the RGB channels, and I want to render a shape to the alpha channel to act as a mask for the image. I know bitmapData has a fillRect(...) function that takes a uint color value, but it seems impossible to apply a color exclusively to the alpha channel without harming the rgb channels. I suppose I could always create a copy bitmap and use it as the alpha channel, but that's a huge waste. Any ideas on the best method of doing this? Thanks in advance. Rate++ for any help (if you care).

Have you looked into the ColorTransform or CopyChannel functions already?