imwdc.object           package:wavethresh           R Documentation

_T_w_o-_d_i_m_e_n_s_i_o_n_a_l _c_o_m_p_r_e_s_s_e_d _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 

     'imwdc'

     They represent a decomposition of an image with respect to a
     two-dimensional wavelet basis

_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. 

     To uncompress this class of object back into an object of class
     'imwd.object' use the 'uncompress.imwdc' function.

_V_a_l_u_e:

     The following components must be included in a legitimate `imwdc'
     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. Note that imwdc objects do not contain scaling
          function coefficients. This would negate the point of having
          a compressed object.

          Each vector stores its coefficients using an object of class
          compressed, i.e. the vector is run-length encoded on zeroes.

          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 'threshold.imwd'
     function to represent a thresholded two-dimensional wavelet
     decomposition of a function. Some other functions return an object
     of class imwdc.

_M_E_T_H_O_D_S:

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

_R_E_L_E_A_S_E:

     Version 3.5.3 Copyright Guy Nason 1994

_S_e_e _A_l_s_o:

     'imwd' 'imwd.object', 'threshold.imwd', 'uncompress.imwdc'.

