.TH IM_OFFSETS45 3 "28 May 1991"
.SH NAME
im_offsets45, im_offsets90, im_rotate_imask45, im_rotate_dmask45,
im_rotate_imask90, im_rotate_dmask90 \- rotate square masks
.SH SYNOPSIS

.B int *im_offsets45( size )
.br
.B int size;

.B int *im_offsets90( size )
.br
.B int size;

.B INTMASK *im_rotate_imask45( m, name )
.br
.B INTMASK *m;
.br
.B char *name;

.B DOUBLEMASK *im_rotate_dmask45( m, name )
.br
.B DOUBLEMASK *m;
.br
.B char *name;

.B INTMASK *im_rotate_imask90( m, name )
.br
.B INTMASK *m;
.br
.B char *name;

.B DOUBLEMASK *im_rotate_dmask90( m, name )
.br
.B DOUBLEMASK *m;
.br
.B char *name;

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

.B 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.

.B 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.

.B 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.

.B 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.

.B 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.

.B 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.

.SH RETURN VALUE
.SH 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).
.SH COPYRIGHT
.br
N. Dessipris
.SH AUTHOR
N. Dessipris \-28/05/1991