inT16 POLY_BLOCK::winding_number(const ICOORD &point) {
inT16 count; //winding count
ICOORD pt; //current point
ICOORD vec; //point to current point
ICOORD vvec; //current point to next point
inT32 cross; //cross product
ICOORDELT_IT it = &vertices; //iterator
count = 0;
do {
pt = *it.data ();
vec = pt - point;
vvec = *it.data_relative (1) - pt;
//crossing the line
if (vec.y () <= 0 && vec.y () + vvec.y () > 0) {
cross = vec * vvec; //cross product
if (cross > 0)
count++; //crossing right half
else if (cross == 0)
return INTERSECTING; //going through point
}
else if (vec.y () > 0 && vec.y () + vvec.y () <= 0) {
cross = vec * vvec;
if (cross < 0)
count--; //crossing back
else if (cross == 0)
return INTERSECTING; //illegal
}
else if (vec.y () == 0 && vec.x () == 0)
return INTERSECTING;
it.forward ();
}
while (!it.at_first ());
return count; //winding number
}
