ref: c6ad540af56be95b458008ae3abd3432b71d49dd
dir: /sys/src/libdraw/bezier.c/
#include <u.h>
#include <libc.h>
#include <draw.h>
#define PINC 32 /* realloc granularity */
typedef struct Plist Plist;
struct Plist
{
Point *p;
int np; /* -1 if malloc/realloc failed */
};
static void
appendpt(Plist *l, Point p)
{
if(l->np == -1)
return;
if(l->np == 0)
l->p = malloc(PINC*sizeof(Point));
else if(l->np%PINC == 0)
l->p = realloc(l->p, (l->np+PINC)*sizeof(Point));
if(l->p == 0){
l->np = -1;
return;
}
l->p[l->np++] = p;
}
static int
normsq(Point p)
{
return p.x*p.x+p.y*p.y;
}
static int
psdist(Point p, Point a, Point b)
{
int num, den;
p = subpt(p, a);
b = subpt(b, a);
num = p.x*b.x + p.y*b.y;
if(num <= 0)
return normsq(p);
den = normsq(b);
if(num >= den)
return normsq(subpt(b, p));
return normsq(subpt(divpt(mulpt(b, num), den), p));
}
/*
* Convert cubic Bezier curve control points to polyline
* vertices. Leaves the last vertex off, so you can continue
* with another curve.
*/
static void
bpts1(Plist *l, Point p0, Point p1, Point p2, Point p3, int scale)
{
Point p01, p12, p23, p012, p123, p0123;
Point tp0, tp1, tp2, tp3;
tp0=divpt(p0, scale);
tp1=divpt(p1, scale);
tp2=divpt(p2, scale);
tp3=divpt(p3, scale);
if(psdist(tp1, tp0, tp3)<=1 && psdist(tp2, tp0, tp3)<=1){
appendpt(l, tp0);
appendpt(l, tp1);
appendpt(l, tp2);
}
else{
/*
* if scale factor is getting too big for comfort,
* rescale now & concede the rounding error
*/
if(scale>(1<<12)){
p0=tp0;
p1=tp1;
p2=tp2;
p3=tp3;
scale=1;
}
p01=addpt(p0, p1);
p12=addpt(p1, p2);
p23=addpt(p2, p3);
p012=addpt(p01, p12);
p123=addpt(p12, p23);
p0123=addpt(p012, p123);
bpts1(l, mulpt(p0, 8), mulpt(p01, 4), mulpt(p012, 2), p0123, scale*8);
bpts1(l, p0123, mulpt(p123, 2), mulpt(p23, 4), mulpt(p3, 8), scale*8);
}
}
static void
bpts(Plist *l, Point p0, Point p1, Point p2, Point p3)
{
bpts1(l, p0, p1, p2, p3, 1);
}
static void
bezierpts(Plist *l, Point p0, Point p1, Point p2, Point p3)
{
bpts(l, p0, p1, p2, p3);
appendpt(l, p3);
}
static void
_bezsplinepts(Plist *l, Point *pt, int npt)
{
Point *p, *ep;
Point a, b, c, d;
int periodic;
if(npt<3)
return;
ep = &pt[npt-3];
periodic = eqpt(pt[0], ep[2]);
if(periodic){
a = divpt(addpt(ep[1], pt[0]), 2);
b = divpt(addpt(ep[1], mulpt(pt[0], 5)), 6);
c = divpt(addpt(mulpt(pt[0], 5), pt[1]), 6);
d = divpt(addpt(pt[0], pt[1]), 2);
bpts(l, a, b, c, d);
}
for(p=pt; p<=ep; p++){
if(p==pt && !periodic){
a = p[0];
b = divpt(addpt(p[0], mulpt(p[1], 2)), 3);
}
else{
a = divpt(addpt(p[0], p[1]), 2);
b = divpt(addpt(p[0], mulpt(p[1], 5)), 6);
}
if(p==ep && !periodic){
c = divpt(addpt(mulpt(p[1], 2), p[2]), 3);
d = p[2];
}
else{
c = divpt(addpt(mulpt(p[1], 5), p[2]), 6);
d = divpt(addpt(p[1], p[2]), 2);
}
bpts(l, a, b, c, d);
}
appendpt(l, d);
}
int
bezsplinepts(Point *pt, int npt, Point **pp)
{
Plist l;
l.np = 0;
l.p = nil;
_bezsplinepts(&l, pt, npt);
*pp = l.p;
return l.np;
}
int
bezier(Image *dst, Point p0, Point p1, Point p2, Point p3, int end0, int end1, int radius, Image *src, Point sp)
{
return bezierop(dst, p0, p1, p2, p3, end0, end1, radius, src, sp, SoverD);
}
int
bezierop(Image *dst, Point p0, Point p1, Point p2, Point p3, int end0, int end1, int radius, Image *src, Point sp, Drawop op)
{
Plist l;
l.np = 0;
bezierpts(&l, p0, p1, p2, p3);
if(l.np == -1)
return 0;
if(l.np != 0){
polyop(dst, l.p, l.np, end0, end1, radius, src, addpt(subpt(sp, p0), l.p[0]), op);
free(l.p);
}
return 1;
}
int
bezspline(Image *dst, Point *pt, int npt, int end0, int end1, int radius, Image *src, Point sp)
{
return bezsplineop(dst, pt, npt, end0, end1, radius, src, sp, SoverD);
}
int
bezsplineop(Image *dst, Point *pt, int npt, int end0, int end1, int radius, Image *src, Point sp, Drawop op)
{
Plist l;
l.np = 0;
_bezsplinepts(&l, pt, npt);
if(l.np==-1)
return 0;
if(l.np != 0){
polyop(dst, l.p, l.np, end0, end1, radius, src, addpt(subpt(sp, pt[0]), l.p[0]), op);
free(l.p);
}
return 1;
}
int
fillbezier(Image *dst, Point p0, Point p1, Point p2, Point p3, int w, Image *src, Point sp)
{
return fillbezierop(dst, p0, p1, p2, p3, w, src, sp, SoverD);
}
int
fillbezierop(Image *dst, Point p0, Point p1, Point p2, Point p3, int w, Image *src, Point sp, Drawop op)
{
Plist l;
l.np = 0;
bezierpts(&l, p0, p1, p2, p3);
if(l.np == -1)
return 0;
if(l.np != 0){
fillpolyop(dst, l.p, l.np, w, src, addpt(subpt(sp, p0), l.p[0]), op);
free(l.p);
}
return 1;
}
int
fillbezspline(Image *dst, Point *pt, int npt, int w, Image *src, Point sp)
{
return fillbezsplineop(dst, pt, npt, w, src, sp, SoverD);
}
int
fillbezsplineop(Image *dst, Point *pt, int npt, int w, Image *src, Point sp, Drawop op)
{
Plist l;
l.np = 0;
_bezsplinepts(&l, pt, npt);
if(l.np == -1)
return 0;
if(l.np > 0){
fillpolyop(dst, l.p, l.np, w, src, addpt(subpt(sp, pt[0]), l.p[0]), op);
free(l.p);
}
return 1;
}