Figure 2 Boolean truth table for gray-scale images

a  b  a AND b  a OR b  a XOR b  a NAND b  a NOR b  NOT a
0  0     0        0       0       value     value  value
0  b     0        a       a       value       0    value
a  0     0        a       a       value       0      0
a  b     a        a       0         0         0      0