Polylines
_clipper_pl(ClipperLib::ClipType clipType, const Polygons &subject,
const Polygons &clip, bool safety_offset_)
{
// transform input polygons into polylines
Polylines polylines;
polylines.reserve(subject.size());
for (Polygons::const_iterator polygon = subject.begin(); polygon != subject.end(); ++polygon)
polylines.push_back(*polygon); // implicit call to split_at_first_point()
// perform clipping
Polylines retval = _clipper_pl(clipType, polylines, clip, safety_offset_);
/* If the split_at_first_point() call above happens to split the polygon inside the clipping area
we would get two consecutive polylines instead of a single one, so we go through them in order
to recombine continuous polylines. */
for (size_t i = 0; i < retval.size(); ++i) {
for (size_t j = i+1; j < retval.size(); ++j) {
if (retval[i].points.back().coincides_with(retval[j].points.front())) {
/* If last point of i coincides with first point of j,
append points of j to i and delete j */
retval[i].points.insert(retval[i].points.end(), retval[j].points.begin()+1, retval[j].points.end());
retval.erase(retval.begin() + j);
--j;
} else if (retval[i].points.front().coincides_with(retval[j].points.back())) {
/* If first point of i coincides with last point of j,
prepend points of j to i and delete j */
retval[i].points.insert(retval[i].points.begin(), retval[j].points.begin(), retval[j].points.end()-1);
retval.erase(retval.begin() + j);
--j;
} else if (retval[i].points.front().coincides_with(retval[j].points.front())) {
/* Since Clipper does not preserve orientation of polylines,
also check the case when first point of i coincides with first point of j. */
retval[j].reverse();
retval[i].points.insert(retval[i].points.begin(), retval[j].points.begin(), retval[j].points.end()-1);
retval.erase(retval.begin() + j);
--j;
} else if (retval[i].points.back().coincides_with(retval[j].points.back())) {
/* Since Clipper does not preserve orientation of polylines,
also check the case when last point of i coincides with last point of j. */
retval[j].reverse();
retval[i].points.insert(retval[i].points.end(), retval[j].points.begin()+1, retval[j].points.end());
retval.erase(retval.begin() + j);
--j;
}
}
}
return retval;
}
Lines
_clipper_ln(ClipperLib::ClipType clipType, const Lines &subject, const Polygons &clip,
bool safety_offset_)
{
// convert Lines to Polylines
Polylines polylines;
polylines.reserve(subject.size());
for (Lines::const_iterator line = subject.begin(); line != subject.end(); ++line)
polylines.push_back(*line);
// perform operation
polylines = _clipper_pl(clipType, polylines, clip, safety_offset_);
// convert Polylines to Lines
Lines retval;
for (Polylines::const_iterator polyline = polylines.begin(); polyline != polylines.end(); ++polyline)
retval.push_back(*polyline);
return retval;
}
Lines
_clipper_ln(ClipperLib::ClipType clipType, const Lines &subject, const Polygons &clip,
bool safety_offset_)
{
// convert Lines to Polylines
Polylines polylines;
polylines.reserve(subject.size());
for (const Line &line : subject)
polylines.emplace_back(Polyline(line.a, line.b));
// perform operation
polylines = _clipper_pl(clipType, polylines, clip, safety_offset_);
// convert Polylines to Lines
Lines retval;
for (Polylines::const_iterator polyline = polylines.begin(); polyline != polylines.end(); ++polyline)
retval.emplace_back(polyline->operator Line());
return retval;
}