edgeFeatures             package:EBImage             R Documentation

_E_x_t_r_a_c_t_i_o_n _o_f _e_d_g_e _p_r_o_f_i_l_e_s _a_n_d _e_d_g_e _f_e_a_t_u_r_e_s _f_r_o_m _i_m_a_g_e_s _o_f _i_n_d_e_x_e_d _o_b_j_e_c_t_s

_D_e_s_c_r_i_p_t_i_o_n:

     Edge profile is a distance profile from the geometric center of
     the object to all its perimeter points calculated by taking the
     distance at different rotation angles (rotation around the
     center). The profile is calculated for the rotation angle, theta
     in '[-pi,pi]'.

_U_s_a_g_e:

       ## S4 method for signature 'IndexedImage':
       edgeProfile(x, ref, n=32, fft=TRUE, scale=TRUE, rotate=TRUE, ...)
       ## S4 method for signature 'IndexedImage':
       edgeFeatures(x, ref, ...)

_A_r_g_u_m_e_n_t_s:

       x: An object of 'IndexedImage'.

     ref: A reference Grayscale image of the same size as 'x'. See
          details.

       n: An integer value giving the number of angle measures. The
          full circle of '[-pi,pi]' is divided into 'n-1' segments, at
          which edges the profile is approximated. 

     fft: A logical value. If 'TRUE', the resulting profile is the
          'fft' transformation of the distance profile giving the
          frequences of angular changes in shape. 

   scale: A logical value. If 'TRUE', the resulting profile is scaled
          by the effective radius (calcualted as part of
          'link{hull.features}') making the profile scale invariant. 

  rotate: A logical value. If 'TRUE', the resulting profile is shifted
          by the object's roation angle (calculated from the 'moments'
          on the 'ref' image, if provided, and on the hull otherwise. 

     ...: Reserved. 

_D_e_t_a_i_l_s:

     The 'ref' image can be omitted. However, if supplied it affects
     the centers of objects and their angles of rotation as in
     'moments'.

     The 'edge.features' runs with 'n=16' calculating scale and
     rotation invariant features. From the original distance profile,
     it returns the measure of object's irregularity taken by
     calculating the difference between the farthest and the closest to
     the center edge points. Then it computes the 'fft' and returns 4
     of it's lowest frequences, corresponding to '2*Pi, 2*Pi/2=Pi,
     2*Pi/3' and '2*Pi/4=Pi/2'.

     The extracted feature names carry a 'e.' prefix to indicate edge
     features.

_V_a_l_u_e:

     For a single frame, both functions return a matrix of descriptors
     with objects in rows and ordered profile points (or features) in
     columns. For image stacks, a list of such matrices.

     The matrix columns in 'edge.profile' correspond, from left to
     right, to the equidistant divisions of the range '[-pi,pi]' if
     'fft' is not used, otherwise to the frequences of angular changes
     (lower frequences on the left, higher on the right up to the
     middle of the vector).

_A_u_t_h_o_r(_s):

     Oleg Sklyar, osklyar@ebi.ac.uk, 2007

_S_e_e _A_l_s_o:

     ' IndexedImage, watershed, getFeatures, hullFeatures, moments '

_E_x_a_m_p_l_e_s:

       ## see example(getFeatures)

