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Transform fill_bits from recursive to iterative

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Avoids crashes when generating polygons from big bitmaps.
This commit is contained in:
Pedro J. Estébanez 2018-08-10 01:37:05 +02:00
parent 42bf5cd790
commit b48d421ca0
1 changed files with 70 additions and 12 deletions
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82
scene/resources/bit_mask.cpp
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@ -418,26 +418,84 @@ static Vector<Vector2> reduce(const Vector<Vector2> &points, const Rect2i &rect,
return result;
}
struct FillBitsStackEntry {
Point2i pos;
int i;
int j;
};
static void fill_bits(const BitMap *p_src, Ref<BitMap> &p_map, const Point2i &p_pos, const Rect2i &rect) {
for (int i = p_pos.x - 1; i <= p_pos.x + 1; i++) {
for (int j = p_pos.y - 1; j <= p_pos.y + 1; j++) {
// Using a custom stack to work iteratively to avoid stack overflow on big bitmaps
PoolVector<FillBitsStackEntry> stack;
// Tracking size since we won't be shrinking the stack vector
int stack_size = 0;
if (i < rect.position.x || i >= rect.position.x + rect.size.x)
continue;
if (j < rect.position.y || j >= rect.position.y + rect.size.y)
continue;
Point2i pos = p_pos;
int next_i;
int next_j;
if (p_map->get_bit(Vector2(i, j)))
continue;
bool reenter = true;
bool popped = false;
do {
if (reenter) {
next_i = pos.x - 1;
next_j = pos.y - 1;
reenter = false;
}
else if (p_src->get_bit(Vector2(i, j))) {
p_map->set_bit(Vector2(i, j), true);
fill_bits(p_src, p_map, Point2i(i, j), rect);
for (int i = next_i; i <= pos.x + 1; i++) {
for (int j = next_j; j <= pos.y + 1; j++) {
if (popped) {
// The next loop over j must start normally
next_j = pos.y;
popped = false;
// Skip because an iteration was already executed with current counter values
continue;
}
if (i < rect.position.x || i >= rect.position.x + rect.size.x)
continue;
if (j < rect.position.y || j >= rect.position.y + rect.size.y)
continue;
if (p_map->get_bit(Vector2(i, j)))
continue;
else if (p_src->get_bit(Vector2(i, j))) {
p_map->set_bit(Vector2(i, j), true);
FillBitsStackEntry se = { pos, i, j };
stack.resize(MAX(stack_size + 1, stack.size()));
stack.set(stack_size, se);
stack_size++;
pos = Point2i(i, j);
reenter = true;
break;
}
}
if (reenter) {
break;
}
}
}
if (!reenter) {
if (stack_size) {
FillBitsStackEntry se = stack.get(stack_size - 1);
stack_size--;
pos = se.pos;
next_i = se.i;
next_j = se.j;
popped = true;
}
}
} while (reenter || popped);
#ifdef DEBUG_ENABLED
print_line("max stack size: " + itos(stack.size()));
#endif
}
Vector<Vector<Vector2> > BitMap::clip_opaque_to_polygons(const Rect2 &p_rect, float p_epsilon) const {
Rect2i r = Rect2i(0, 0, width, height).clip(p_rect);