hullFeatures             package:EBImage             R Documentation

_E_x_t_r_a_c_t_i_o_n _o_f _h_u_l_l _f_e_a_t_u_r_e_s _f_r_o_m _i_m_a_g_e _o_b_j_e_c_t_s

_D_e_s_c_r_i_p_t_i_o_n:

     Computes hull features from image objects.

_U_s_a_g_e:

       hullFeatures(x)

_A_r_g_u_m_e_n_t_s:

       x: An 'Image' object or an array containing object masks. Object
          masks are sets of pixels with the same unique integer value.

_D_e_t_a_i_l_s:

     Extracted object features are:

        *  'g.x ,g.y' - coordinates of the geometric center.

        *  'g.s' - size in pixels.

        *  'g.p' - perimeter in pixels. 

        *  'g.pdm' - mean distance from the center to perimeter.

        *  'g.pdsd' - standard deviation of the distance to perimeter.

        *  'g.effr' - effective radius (is the radius of a circle with
           the same area).

        *  'g.acirc' - acircularity (fraction of pixels outside of the
           circle with radius 'g.effr'). 

        *  'g.sf' - shape factor, equals to ('g.p/ ( 2*sqrt(i*g.s))').

        *  'g.edge' - number of pixels at the edge of the image. 

        *  'g.theta' - hull orientation angle, in radians. See above.

        *  'g.l1' - largest eigeinvalue of the covariance matrix. See
           above.

        *  'g.l2' - lowest eigenvalue of the covariance matrix. See
           above.

        *  'g.ecc' - eccentricity, equals to sqrt(1-g.l2/g.l1). See
           above.

        *  'g.I1, g.I2' - first and second Hu's
           translation/scale/rotation invariant moment. See above.

     The features 'g.theta', 'g.l1', 'g.l2', 'g.ecc', 'g.I1',  'g.I2'
     are computed with the function 'moments' using the binary objects
     as intensity values, e.g. 'g.theta = moment(x,x>0)[, 'm.theta']'.
     See 'moments' for details  on properties of these features.

_V_a_l_u_e:

     A matrix (or a list of matrices if 'x' contains multiple frames)
     of features computed of the objects present in 'x'.

_A_u_t_h_o_r(_s):

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

_S_e_e _A_l_s_o:

     'moments', 'getFeatures'

_E_x_a_m_p_l_e_s:

       x = readImage(system.file('images', 'shapes.png', package='EBImage'))
       x = x[110:512,1:130]
       y = bwlabel(x)
       if (interactive()) display(normalize(y), title='Objects')

       ## hullFeatures
       hf = hullFeatures(y)
       print(hf)
             

