  An integral of the Wigner function of a wavefunction |psi >, over some region
S in classical phase space is identified as a (quasi) probability measure (QPM)
of S, and it can be expressed by the |psi > average of an operator referred to
as the region operator (RO). Transformation theory is developed which provides
the RO for various phase space regions such as point, line, segment, disk and
rectangle, and where all those ROs are shown to be interconnected by completely
positive trace increasing maps. The latter are realized by means of unitary
operators in Fock space extended by 2D vector spaces, physically identified
with finite dimensional systems. Bounds on QPMs for regions obtained by tiling
with discs and rectangles are obtained by means of majorization theory.
