.TH IM_SGLDS_MATRIX 3 "10 May 1991"
.SH 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
.SH SYNOPSIS
.B #include <vips/vips.h>

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

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

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

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

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

.SH DESCRIPTION
.B 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.

.B 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.

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

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

.B im_glds_mean()
calculates the mean of the sglds matrix held by m.  The result is returned
into the location pointed by mean.
.SH RETURNED VALUES
All functions returns 0 on success and -1 on error.
.SH SEE\ ALSO
im_cooc_matrix(3)
.SH COPYRIGHT
.br
N. Dessipris
.SH AUTHOR
N. Dessipris \- 10/05/1991