Bezier* bezier_subrange(Bezier* b, float t1, float t2)
{
Bezier* left = 0;
Bezier* middle_and_right = 0;
Bezier* middle = 0;
Bezier* right = 0;
bezier_split(b, t1, &left, &middle_and_right);
bezier_split(middle_and_right, t2, &middle, &right);
bezier_destroy(left);
bezier_destroy(middle_and_right);
bezier_destroy(right);
return middle;
}
static bool test_bezier_split(void)
{
double coords[5] = { 0., 1., 0.5, 1., 0.5 };
double coordsA[5];
double coordsB[5];
bezier_split(0.5, 4, coordsA, coordsB, coords);
double err = 0.;
for (double x = 0.; x < 1.; x += 0.01) {
double a = bezier_curve(x, 4, coords);
double b = (x <= 0.5) ? bezier_curve(2. * x, 4, coordsA)
: bezier_curve(2. * (x - 0.5), 4, coordsB);
err += pow(a - b, 2);
}
return (err < 1.E-28);
}
/*!
* Given the original segments and splits apply
* all segment splits and create unique segment index.
*
* Split.seg is the index to the segment to split before this function.
* After the splits are applied every split.seq is unique.
*/
static void
_split_segments (GArray *segs, GArray *splits, const GArray *other)
{
int i, sofs = 0;
GArray *pending;
/* splits must be sorted for the algorithm below */
g_array_sort (splits, _compare_split);
for (i = 0; i < splits->len; ++i) {
int j, to;
int from = i;
int from_seg = g_array_index (splits, Split, i).seg;
BezierSegment bs;
real t = 0;
g_return_if_fail (from_seg + sofs < segs->len);
bs = g_array_index (segs, BezierSegment, from_seg + sofs);
while (i < splits->len - 1 && from_seg == g_array_index (splits, Split, i+1).seg)
++i; /* advance while segment reference is the same */
to = i;
for (j = from; j <= to; j++) {
BezierSegment left, right;
/* scale t to split the right segment */
real tL = g_array_index (splits, Split, j).split;
real tR = (tL - t) / (1.0 - t);
bezier_split_at (&bs, &left, &right, tR);
bs = right;
t = tL;
/* overwrite the exisiting */
g_return_if_fail (from_seg + sofs < segs->len);
g_array_index (segs, BezierSegment, from_seg + sofs) = left;
sofs += 1; /* increment segment offset for every segment added */
/* insert a new one behind that ... */
g_array_insert_val (segs, from_seg + sofs, right); /* ... potentially overwritten */
/* adjust the segment reference */
g_array_index (splits, Split, j).seg = from_seg + sofs;
}
}
pending = g_array_new (FALSE, FALSE, sizeof(BezierSegment));
/* for every sub-path determine if it is inside the full other path */
for (i = 0; i < splits->len; ++i) {
Split *sp = &g_array_index (splits, Split, i);
BezierSegment *bs = &g_array_index (segs, BezierSegment, sp->seg);
BezierSegment left, right;
int to, j;
if (i == 0 && sp->seg > 0)
g_array_append_vals (pending, &g_array_index (segs, BezierSegment, 0), sp->seg);
bezier_split (bs, &left, &right);
sp->outside = distance_bez_shape_point (&g_array_index (other, BezPoint, 0), other->len,
0 /* line width */, &right.p0) > 0.0;
/* also remember the sub-path */
to = g_array_index (splits, Split, (i+1)%splits->len).seg;
sp->path = g_array_new (FALSE, FALSE, sizeof(BezierSegment));
if (to < sp->seg) {
g_array_append_vals (sp->path, bs, segs->len - sp->seg);
#if 0
/* XXX: this is only correct if there is no move-to within the segments */
g_array_append_vals (sp->path, &g_array_index (segs, BezierSegment, 0), to);
#else
g_array_append_vals (sp->path, &g_array_index (pending, BezierSegment, 0), pending->len);
g_array_set_size (pending, 0);
#endif
} else {
for (j = sp->seg; j < to; ++j) {
if (_segment_is_moveto (bs)) {
g_array_append_vals (sp->path, &g_array_index (pending, BezierSegment, 0), pending->len);
g_array_set_size (pending, 0);
break;
}
g_array_append_val (sp->path, *bs);
bs++;
}
for (/* remains */; j < to; ++j) {
g_array_append_val (pending, *bs);
bs++;
}
}
}
g_array_free (pending, TRUE);
}
/*!
* \brief Calculate crossing points of two bezier segments
*
* Beware two bezier segments can intersect more than once, but this
* function only returns the first or no intersection. It is the
* responsibility of the caller to further split segments until there
* is no intersection left.
*/
static gboolean
bezier_bezier_intersection (GArray *crossing,
const BezierSegment *a,
const BezierSegment *b,
int depth,
real asplit,
real bsplit)
{
Rectangle abox, bbox;
PolyBBExtras extra = { 0, };
gboolean small_a, small_b;
/* Avoid intersection overflow: if start and end are on the other segment
* assume full overlap and no crossing.
*/
if ( (_segment_has_point (a, &b->p0) && _segment_has_point (a, &b->p3))
|| (_segment_has_point (b, &a->p0) && _segment_has_point (b, &a->p3)))
return FALSE; /* XXX: more variants pending, partial overlap */
/* With very similar segments we would create a lot of points with not
* a very deep recursion (test with ying-yang symbol).
* Just comparing the segments on depth=1 is not good enough, so for
* now we are limiting the number of intersections
*/
if (crossing->len > 127) { /* XXX: arbitrary limit */
g_warning ("Crossing limit (%d) reached", crossing->len);
return FALSE;
}
bicubicbezier2D_bbox (&a->p0, &a->p1, &a->p2, &a->p3, &extra, &abox);
bicubicbezier2D_bbox (&b->p0, &b->p1, &b->p2, &b->p3, &extra, &bbox);
if (!rectangle_intersects (&abox, &bbox))
return FALSE;
small_a = (abox.right - abox.left) < EPSILON && (abox.bottom - abox.top) < EPSILON;
small_b = (bbox.right - bbox.left) < EPSILON && (bbox.bottom - bbox.top) < EPSILON;
/* if the boxes are small enough we can calculate the point */
if (small_a && small_b) {
/* intersecting and both small, should not matter which one is used */
Point pt = { (abox.right + abox.left + bbox.right + bbox.left) / 4,
(abox.bottom + abox.top + bbox.bottom + bbox.top) / 4 };
Intersection is;
int i;
for (i = 0; i < crossing->len; ++i) {
/* if it's already included we are done */
if (distance_point_point (&g_array_index (crossing, Intersection, i).pt, &pt) < 1.4142*EPSILON)
return TRUE; /* although we did not add it */
}
is.split_one = asplit;
is.split_two = bsplit;
is.pt = pt;
g_print ("d=%d; as=%g; bs=%g; ", depth, asplit, bsplit);
g_array_append_val (crossing, is);
return TRUE;
} else {
/* further splitting of a and b; it could be smart to only search in the
* intersection of a-box and b-box ... */
BezierSegment a1, a2;
BezierSegment b1, b2;
real ofs = 1.0/(1<<(depth+1));
gboolean ret = FALSE;
bezier_split (a, &a1, &a2);
bezier_split (b, &b1, &b2);
ret |= bezier_bezier_intersection (crossing, &a1, &b1, depth+1, asplit-ofs, bsplit-ofs);
ret |= bezier_bezier_intersection (crossing, &a2, &b1, depth+1, asplit+ofs, bsplit-ofs);
ret |= bezier_bezier_intersection (crossing, &a1, &b2, depth+1, asplit-ofs, bsplit+ofs);
ret |= bezier_bezier_intersection (crossing, &a2, &b2, depth+1, asplit+ofs, bsplit+ofs);
/* XXX: check !ret case, not sure if it should happen */
return ret;
}
}
