.TH Rect 3 "2 May 1991"
.SH NAME
im_rect_marginadjust, im_rect_includespoint, im_rect_includesrect,
im_rect_intersectrect, im_rect_isempty, im_rect_unionrect, im_rect_normalise,
im_rect_equalsrect, im_rect_dup,
IM_RECT_RIGHT, IM_RECT_BOTTOM, IM_RECT_HCENTRE, IM_RECT_VCENTRE
\- rectangle algebra functions
.SH SYNOPSIS
#include <vips/vips.h>
.br
#include <vips/rect.h>
 
typedef struct {
.br
	int left, top, width, height;
.br
} Rect;

#define IM_RECT_RIGHT(R) ((R)->left + (R)->width)
.br
#define IM_RECT_BOTTOM(R) ((R)->top + (R)->height)
.br
#define IM_RECT_HCENTRE(R) ((R)->left + (R)->width / 2)
.br
#define IM_RECT_VCENTRE(R) ((R)->top + (R)->height / 2)

void im_rect_marginadjust( Rect *r, int n );
.br
int im_rect_includespoint( Rect *r, int x, int y );
.br
int im_rect_includesrect( Rect *r1, Rect *r2 );
.br
void im_rect_intersectrect( Rect *r1, Rect *r2, Rect *r3 );
.br
int im_rect_isempty( Rect *r );
.br
void im_rect_unionrect( Rect *r1, Rect *r2, Rect *r3 );
.br
int im_rect_equalsrect( Rect *r1, Rect *r2 );
.br
Rect *im_rect_dup( Rect *r );
.br
void im_rect_normalise( Rect *r );
.SH DESCRIPTION
These functions perform simple algebra on Rect structs. There should also be a
set of functions to do rectlist algebra.

im_rect_marginadjust(3) expands a Rect by n units up, down, left and right.
Negative expansions shrink the Rect.  

im_rect_includespoint(3) returns non-zero
if point (x,y) lies within Rect r.  

im_rect_includesrect(3) returns non-zero if
Rect r2 lies completely within Rect r1.  

im_rect_intersectrect(3) fills Rect r3
with the intersection of Rects r1 and r2.  

im_rect_isempty(3) returns non-zero
if Rect r has either width less than or equal to 0 or height less than or
equal to 0. 

im_rect_unionrect(3) fills Rect r3 with the bounding box of Rect r1 and Rect
r2. A proper union operation requires lists of rectangles, sadly.

im_rect_equalsrect(3) returns non-zero if r1 and r2 are identical.

im_rect_dup(3) allocates memory for a new Rect structure and copies the
elements of r into it. It returns a pointer to the new struct, or NULL on
error.

im_rect_normalise(3) flips r so that the same pixels are enclosed, 
but width and height are guaranteed >=0.

.SH SEE ALSO
im_prepare(3), im_region_create(3)
.SH COPYRIGHT
National Gallery, 1992
.SH AUTHOR
J. Cupitt