/*! For the oCCW (positive) polygon orientation a positive dOff will
inflate the polygon. For the oCW (negative) polygon orientation
a positive dOff will shrink the polygon.
*/
void Polygon2D::Offset(
qreal dOff //!< Offset value.
)
{
VecVertex vecNew;
vecNew.reserve(GetCount());
// Move each point
for(unsigned int i=0; i<GetCount(); i++) {
Line2D lnA = GetLine(i==0 ? GetCount()-1 : i-1);
Line2D lnB = GetLine(i);
// Offset both lines
lnA.Offset(-dOff);
lnB.Offset(-dOff);
// Intersection gives the new point;
Point2D ptI;
unsigned int uStatus = lnA.GetIntersection(lnB, ptI);
if(uStatus & Line2D::intExist) {
vecNew.push_back(ptI);
}
// lnA and lnB are parallel
else {
vecNew.push_back(lnA.GetB());
}
}
Clear();
m_vecV = vecNew;
}
/*! First all intersections are calculated. Then duplicates are removed.
If only points on the line are required, all points that are outside
the lnX[A,B] are removed. If bParallel is true, parallel segmets are
checked for overlap and overlap points are included in the solution.
\retval VecVertex container of intersection points.
*/
QVector<Point2D> Polygon2D::GetIntersection(
const Line2D& lnX, //!< line that intersects the polygon
bool bOnLineOnly, //!< if true, only points between A and B inclusive are counted.
bool bParallel //!< check parallel lines for overlap
) const
{
// results are stored here
QVector<Point2D> vecInt;
// for each segment
for(unsigned int i=0; i<GetCount(); i++) {
Line2D ln = GetLine(i);
Q_ASSERT(ln.IsValid());
Point2D ptInt;
// Check overlaps, if they are wanted
if(bParallel && ln.IsParallel(lnX)) {
Line2D lnO = ln.GetOverlap(lnX);
if(lnO.IsValid()) {
vecInt.push_back(lnO.GetA());
vecInt.push_back(lnO.GetB());
}
}
// check intersections
if(ln.GetIntersection(lnX, ptInt) & Line2D::intFirst){
vecInt.push_back(ptInt);
}
}
// Sort the points in the vector. Same point may appear several
// times.
Point2DSortLineLess pred(lnX);
std::sort(vecInt.begin(),vecInt.end(),pred);
// remove duplicates, if any
QVector<Point2D>::iterator f = std::unique(vecInt.begin(),vecInt.end());
vecInt.erase(f,vecInt.end());
// remove all points that are not inside the line
if(bOnLineOnly) {
QVector<Point2D>::iterator i=vecInt.begin();
while(i!=vecInt.end()) {
if(!(lnX.GetPosition(*i) & Line2D::posInsideEnd))
i = vecInt.erase(i);
else
i++;
}
}
return vecInt;
}
