imwd.object            package:wavethresh            R Documentation

_T_w_o-_d_i_m_e_n_s_i_o_n_a_l _w_a_v_e_l_e_t _d_e_c_o_m_p_o_s_i_t_i_o_n _o_b_j_e_c_t_s.

_D_e_s_c_r_i_p_t_i_o_n:

     These are objects of classes 

     'imwd'

     They represent a decomposition of an image with respect to a
     two-dimensional wavelet basis (or tight frame in the case of the
     two-dimensional (space-ordered) non-decimated wavelet
     decomposition).

_D_e_t_a_i_l_s:

     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.

_V_a_l_u_e:

     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. 

    type: If 'type="wavelet"' then the image was decomposed according
          to the 2D Mallat pyramidal algorithm. If 'type="station"'
          then the image was decomposed using the 2D spatially ordered
          non-decimated wavelet transform.

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. See the help for
          'first.last' if you are a masochist. 

     _f_i_l_t_e_r A filter object as returned by the 'filter.select'
          function. This component records the filter used in the
          decomposition. The reconstruction routines use this component
          to find out what filter to use in reconstruction. 

     _w_N_L_x 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 and "4" corresonding to scaling function
          coefficients at the given resolution level. 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. 

          Note that if 'type="wavelet"' then images at level N are
          subimages of side length '2^N' pixels. If the type component
          is '"station"' then each coefficient subimage is of the same
          dimension as the input image used to create this object.

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.

_G_E_N_E_R_A_T_I_O_N:

     This class of objects is returned from the 'imwd' function to
     represent a two-dimensional (possibly space-ordered non-decimated)
     wavelet decomposition of a function. Many other functions return
     an object of class imwd.

_M_E_T_H_O_D_S:

     The imwd class of objects has methods for the following generic
     functions: 'compress', 'draw', 'imwr', 'nullevels.imwd', 'plot',
     'print', 'summary', 'threshold.imwd'.

_R_E_L_E_A_S_E:

     Version 3.5.3 Copyright Guy Nason 1994

_S_e_e _A_l_s_o:

     'imwd'

