subspace for an image at resolution j is denoted V
2
j
, which is in L
2
(R
2
),
and its orthogonal complement subspace is denoted W
2
j
. As with one-dimensional
multiresolution spaces, the sum of the subspaces V
2
j
and W
2
j
forms the
finer approximation space V
2
jþ1
;thatis,
V
2
jþ1
¼ V
2
j
W
2
j
(7:69)
To construct two-dimensional wavelet bases, we first consider the separable
basis, which is obtained by applying the same filters developed for one-
dimensional signals to each dimension separately. In vector spaces, the separable
two-dimensional multiresolution space is defined by the tensor product of
one-dimensional multiresolution spaces,
V
2
j
¼ V
j
V
j
(7:70)
Thus the separable two-dimensional scaling function can be written as
f(x, y) ¼ f(x)f(y)(7:71)
which means that one can ...