imwd.object {wavethresh} | R Documentation |
These are objects of class "imwd"
.
They represent a decomposition of a 2D function with respect
to a 2D wavelet basis.
In previous releases the original image was stored as the "original" component of a imwd object. This is not done now as the resulting objects were excessively large.
The following components must be included in a legitimate imwd
object.
nlevels |
number of levels in wavelet decomposition. If you raise 2 to the power of nlevels then you get the dimension of the image that you originally started with. |
fl.dbase |
The first last database associated with the decomposition. For images, this list is not very useful as each level's components is stored as a list component, rather than being packaged up in a single vector as in the 1D case. Nevertheless the internals still need to know about fl.dbase to get the computations correct. |
filter |
A filter object as returned by "filter.select". This component records the filter used in the decomposition. The reconstruction routines use this component to find out what filter to use in reconstruction. |
wNLx |
The object will probably contain many components with names of
this form. These are all the wavelet coefficients of the decomposition.
In "wNLx" the "N" refers to the level number and the "x" refers to
the direction of the coefficients with "1" being horizontal,
"2" being vertical and "3" being diagonal. Note that the levels
should be in numerically decreasing order, so if nlevels is 5, then
there will be w5L1, w5L2, w5L3 first, then down to w1L1, w1L2, and
w1L3. Note that these coefficients store their data according to
the first.last database fl.dbase$first.last.d , so refer to
them using this, see first.last .
|
w0Lconstant |
This is the coefficient of the bottom level scaling function coefficient. So for example, if you used Haar wavelets this would be the sample mean of the data (scaled by some factor depending on the number of levels, nlevels). |
bc |
This component details how the boundaries were treated in the decomposition. |
This class of objects is typically returned from imwd(.)
to represent a wavelet decomposition of an image (or other 2D function).
The "imwd"
class of objects has methods for the following generic
functions:
plot
, threshold
, summary
, print
, draw
, imwr
, compress
.
Release 2.2 Copyright Guy Nason 1993
imwd
for examples;
compress
, draw
.