The alpha channel ones would not apply to printing, and overall printing is an extremely lossy operation, where all those minute details get washed out in approximate ink levels and the muddiness of the physical world. It might not be totally foolproof, esp for a very accurate print process (don't use your photo printer maybe), but it's probably many orders of magnitude noisier..

I think if you're really concerned, you'd print it once, apply physical black tape on it (or cut out with a razor), then scan that :)

Printing would presumably have enough imprecision to mask those.