ADDPT(3)

NAME
addpt, subpt, mulpt, divpt, rectaddpt, rectsubpt, insetrect, canonrect, eqpt, eqrect, ptinrect, rectinrect, rectXrect, rectclip, combinerect, Dx, Dy, Pt, Rect, Rpt - arithmetic on points and rectangles

SYNOPSIS
#include <u.h>
#include <libc.h>
#include <draw.h>

Point    addpt(Point p, Point q)

Point    subpt(Point p, Point q)

Point    mulpt(Point p, int a)

Point    divpt(Point p, int a)

Rectangle    rectaddpt(Rectangle r, Point p)

Rectangle    rectsubpt(Rectangle r, Point p)

Rectangle    insetrect(Rectangle r, int n)

Rectangle    canonrect(Rectangle r)

int    eqpt(Point p, Point q)

int    eqrect(Rectangle r, Rectangle s)

int    ptinrect(Point p, Rectangle r)

int    rectinrect(Rectangle r, Rectangle s)

int    rectXrect(Rectangle r, Rectangle s)

int    rectclip(Rectangle *rp, Rectangle b)

void    combinerect(Rectangle *rp, Rectangle b)

int    Dx(Rectangle r)

int    Dy(Rectangle r)

Point    Pt(int x, int y)

Rectangle    Rect(int x0, int y0, int x1, int y1)

Rectangle    Rpt(Point p, Point q)

DESCRIPTION
The functions Pt, Rect and Rpt construct geometrical data types from their components.

Addpt returns the Point sum of its arguments: Pt(p.x+q.x, p.y+q.y). Subpt returns the Point difference of its arguments: Pt(p.x-q.x, p.y-q.y). Mulpt returns the Point Pt(p.x*a, p.y*a). Divpt returns the Point Pt(p.x/a, p.y/a).

Rectaddpt returns the Rectangle Rect(add(r.min, p), add(r.max, p)); rectsubpt returns the Rectangle Rpt(sub(r.min, p), sub(r.max, p)).

Insetrect returns the Rectangle Rect(r.min.x+n, r.min.y+n, r.max.x-n, r.max.y-n).

Canonrect returns a rectangle with the same extent as r, canonicalized so that min.x ≤ max.x, and min.y ≤ max.y.

Eqpt compares its argument Points and returns 0 if unequal, 1 if equal. Eqrect does the same for its argument Rectangles.

Ptinrect returns 1 if p is a point within r, and 0 otherwise.

Rectinrect returns 1 if all the pixels in r are also in s, and 0 otherwise.

RectXrect returns 1 if r and s share any point, and 0 otherwise.

Rectclip clips in place the Rectangle pointed to by rp so that it is completely contained within b. The return value is 1 if any part of *rp is within b. Otherwise, the return value is 0 and *rp is unchanged.

Combinerect overwrites *rp with the smallest rectangle sufficient to cover all the pixels of *rp and b.

The functions Dx and Dy give the width (Δx) and height (Δy) of a Rectangle. They are implemented as macros.

SOURCE
/usr/local/plan9/src/libdraw

SEE ALSO
graphics(3)