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NAME

       im_eye, im_feye - creates a pattern which shows the spatial response of
       the human visual system

SYNOPSIS

       #include <vips/vips.h>

       int im_eye(image, xsize, ysize, factor)
       IMAGE *image;
       int xsize, ysize;
       double factor;

       int im_feye(image, xsize, ysize, factor)
       IMAGE *image;
       int xsize, ysize;
       double factor;

DESCRIPTION

       im_feye() creates an one band float image with pels  in  [-1,+1]  of  a
       pattern which has the following properties:
       - the spatial frequency increases from left to right.
       - the grey level intensity decreases from top to bottom.
       The sizes of the produced image are determined by the entered arguments
       xsize and ysize.  The variable factor which should be between 0 and  1,
       determines  the number of maximum spatial frequencies present along the
       horizontal direction.

       im_eye() behaves  exactly  as  im_feye(),  but  scales  the  output  to
       [0,255].

RETURN VALUE

       The function returns 0 on success and -1 on error.

SEE ALSO

       im_grey(3), im_zone(3).

COPYRIGHT

       N. Dessipris

AUTHOR

       N. Dessipris - 10/05/1991

                                  10 May 1991