extracts a selected set of discrete wavelet transform (DWT) coefficients from the full set of coefficients stored in compact form, as computed by c09ecf
is intended to be used after a call to c09ecf
(two-dimensional DWT), which in turn should be preceded by a call to c09abf
(two-dimensional wavelet filter initialization). Given an initial two-dimensional data set
, a prior call to c09ecf
computes the approximation coefficients (at the highest requested level) and three sets of detail coeficients at all levels and stores these in compact form in a one-dimensional array c
can then extract either the approximation coefficients or one of the sets of detail coefficients at one of the levels into a matrix
. The dimensions of
depend on the level extracted and are available from the arrays dwtlvm
as returned by c09ecf
which contain the first and second dimensions respectively. See Section 2.1
in the C09 Chapter Introduction for a discussion of the two-dimensional DWT.
the following notation is used in this section:
- is the number of wavelet coefficients in the first dimension, which, at level ilev, is equal to as returned by a call to c09ecf transforming nwl levels.
- is the number of wavelet coefficients in the second dimension, which, at level ilev, is equal to as returned by a call to c09ecf transforming nwl levels.
If on entry
, explanatory error messages are output on the current error message unit (as defined by x04aaf