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NAME

       im_offsets45,   im_offsets90,   im_rotate_imask45,   im_rotate_dmask45,
       im_rotate_imask90, im_rotate_dmask90 - rotate square masks

SYNOPSIS

       int *im_offsets45( size )
       int size;

       int *im_offsets90( size )
       int size;

       INTMASK *im_rotate_imask45( m, name )
       INTMASK *m;
       char *name;

       DOUBLEMASK *im_rotate_dmask45( m, name )
       DOUBLEMASK *m;
       char *name;

       INTMASK *im_rotate_imask90( m, name )
       INTMASK *m;
       char *name;

       DOUBLEMASK *im_rotate_dmask90( m, name )
       DOUBLEMASK *m;
       char *name;

DESCRIPTION

       These functions can be used to produce the integer  offsets  needed  to
       rotate masks by 45 or 90 degrees clockwise.

       im_offsets45()  accepts  only even size and returns a pointer to an int
       buffer of size*size.  The program mallocs the buffer and puts  into  it
       the  integer  offsets  needed  to rotate a mask of even size size by 45
       degrees.  For instance if size is 3 the program returns the buffer 3  0
       1   6  4  2   7  8  5 which is the offsets needed to rotate a mask with
       offsets 0 1 2  3 4 5  6 7 8.  The function return a  pointer  to  valid
       data  on success or NULL on error.  Since the program mallocs a buffer,
       the user should free the returned pointer accordingly.

       im_offsets90() accepts any size and returns a pointer to an int  buffer
       of  size*size.   The  program  mallocs  the buffer and puts into it the
       integer offsets needed to rotate a mask of size  size  by  90  degrees.
       For  instance  if size is 3 the program returns the buffer 6 3 0  7 4 1
       8 5 2 which is the offsets needed to rotate a mask with offsets 0  1  2
       3  4 5  6 7 8.  The function return a pointers to valid data on success
       or NULL on error.  Since the program mallocs a buffer, the user  should
       free the returned pointer accordingly.

       im_rotate_imask45() rotates the INTMASK m by 45 degrees and returns the
       rotated mask.  The filename member of the returned structure is set  to
       name.   The program allocates memory for the new mask and therefore the
       user must free the returned mask by a call  to  im_free_imask(3).   The
       returned  mask is rotated by 45 degrees clockwise.  The function return
       a valid INTMASK pointer on success or NULL on error.

       im_rotate_dmask45() rotates the DOUBLEMASK m by 45 degrees and  returns
       the rotated mask.  The filename member of the returned structure is set
       to name.  The program allocates memory for the new mask  and  therefore
       the  user  must  free  the returned mask by a call to im_free_dmask(3).
       The returned mask is rotated by 45  degrees  clockwise.   The  function
       return a valid DOUBLEMASK pointer on success or NULL on error.

       im_rotate_imask90() rotates the INTMASK m by 90 degrees and returns the
       rotated mask.  The filename member of the returned structure is set  to
       name.   The program allocates memory for the new mask and therefore the
       user must free the returned mask by a call  to  im_free_imask(3).   The
       returned  mask is rotated by 90 degrees clockwise.  The function return
       a valid INTMASK pointer on success or NULL on error.

       im_rotate_dmask90() rotates the DOUBLEMASK m by 90 degrees and  returns
       the rotated mask.  The filename member of the returned structure is set
       to name.  The program allocates memory for the new mask  and  therefore
       the  user  must  free  the returned mask by a call to im_free_dmask(3).
       The returned mask is rotated by 90  degrees  clockwise.   The  function
       return a valid DOUBLEMASK pointer on success or NULL on error.

RETURN VALUE

SEE ALSO

       im_read_imask(3), im_read_dmask(3), im_free_imask(3), im_free_dmask(3),
       im_gradient(3), im_compass(3), im_conv(3).

COPYRIGHT

       N. Dessipris

AUTHOR

       N. Dessipris -28/05/1991

                                  28 May 1991                  IM_OFFSETS45(3)