The java.awt.AlphaComposite class currently supports 8 of the 12 rules
that Porter and Duff defined in their paper on compositing:

Clear
A (Src)
A over B (SrcOver)
B over A (DstOver)
A in B (SrcIn)
B in A (DstIn)
A held out by B (SrcOut)
B held out by A (DstOut)

The remaining rules that are defined by Porter and Duff but not
provided by the current implementation are:

B (Dst)
A atop B (SrcAtop)
B atop A (DstAtop)
A xor B (Xor)