2011

In this case, only the alpha portion of the image was manipulated, however,
since a black stroke was used, part of the alpha has become transparent. If a
white stroke were used there would be no change to the alpha. If a color other
than black or white were used, varying transparencies would occur on the
front image and varying shades of gray would result on the alpha.
The next example illustrates layer behavior when the front input image is
combined with its own alpha channel. In this case, a Diamond Keyer is added
to the dependency graph and the blue screen is keyed out of the image.
580 | Chapter 24 Raster Paint