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NAME

       im_glds_matrix,     im_glds_asm,     im_glds_contrast,    im_glds_mean,
       im_glds_entropy - calculate the spatial grey  level  difference  matrix
       and features on it

SYNOPSIS

       #include <vips/vips.h>

       int im_glds_matrix(im, m, xp, yp, xs, ys, dx, dy)
       IMAGE *im, *m;
       int xp, yp, xs, ys;
       int dx, dy;

       int im_glds_asm(m, asmoment)
       IMAGE *m;
       double *asmoment;

       int im_glds_contrast(m, contrast)
       IMAGE *m;
       double *contrast;

       int im_glds_entropy(m, entropy)
       IMAGE *m;
       double *entropy;

       int im_glds_mean(m, mean)
       IMAGE *m;
       double *mean;

DESCRIPTION

       im_glds_matrix()  creates  a  256  by  1 one channel spatial grey level
       difference matrix (sglds) of the box determined by the parameters  (xp,
       yp;  xs,  ys) within the image pointed by the IMAGE descriptor im.  The
       matrix is written onto the IMAGE descriptor m.  The displacement vector
       is  determined  by (dx, dy).  The user must ensure that there is enough
       border pixels around the box within im  dictated  by  the  displacement
       vector  (dx,dy)  or  else  the  program  fails.  im  should be one-band
       unsigned char.

       All entries of the sgld matrix are double normalised to the  number  of
       pairs involved.  This function is a direct implementation of the paper:
       Haralick R.  M., Shanmugan K. and Dinstein I., ’Textural  features  for
       image   classification’,   IEEE   Transactions  on  Systems,  Man,  and
       Cybernetics, Vol.  SMC-3, No 6, Nov. 1973, pp 610-621.

       im_glds_asm() calculates the angular second moment of the co-occurrence
       matrix  held by m.  The result is returned into the location pointed by
       asmoment.

       im_glds_contrast() calculates the contrast of the sglds matrix held  by
       m.  The result is returned into the location pointed by contrast.

       im_glds_entropy() calculates the entropy of the sglds matrix held by m.
       The result is returned into the location pointed by entropy.

       im_glds_mean() calculates the mean of the sglds matrix held by m.   The
       result is returned into the location pointed by mean.

RETURNED VALUES

       All functions returns 0 on success and -1 on error.

SEE ALSO

       im_cooc_matrix(3)

COPYRIGHT

       N. Dessipris

AUTHOR

       N. Dessipris - 10/05/1991

                                  10 May 1991               IM_SGLDS_MATRIX(3)