任意直线分割多边形，返回分割后的多边形

效果

使用示例

QPolygonF LineSegmentationPolygon(const QPolygonF& poly, const QLineF& line, SideToRemove sideToRemove)

源码

	enum class SideToRemove {
		None,
		Left,
		Right
	};

// 直线分割多边形
QPolygonF LineSegmentationPolygon(const QPolygonF& poly, const QLineF& line, SideToRemove sideToRemove) 
{
	auto AppendPointIfDifferent = [](QPolygonF& polygon, const QPointF& point) {
		if (polygon.isEmpty() || polygon.last() != point) {
			polygon << point;
		}
	};

	QPolygonF resultPoly;

	for (int i = 0; i < poly.size(); ++i) {
		QPointF p1 = poly[i];
		QPointF p2 = poly[(i + 1) % poly.size()];

		qreal d1 = line.dx() * (p1.y() - line.y1()) - line.dy() * (p1.x() - line.x1());
		qreal d2 = line.dx() * (p2.y() - line.y1()) - line.dy() * (p2.x() - line.x1());

		if ((sideToRemove == SideToRemove::None) ||
			(sideToRemove == SideToRemove::Left && d1 >= 0) ||
			(sideToRemove == SideToRemove::Right && d1 <= 0)) {
			//resultPoly << p1;
			AppendPointIfDifferent(resultPoly, p1);
		}

		if ((d1 * d2) < 0) {
			qreal x = (p1.x() * d2 - p2.x() * d1) / (d2 - d1);
			qreal y = (p1.y() * d2 - p2.y() * d1) / (d2 - d1);
			//resultPoly << QPointF(x, y);
			AppendPointIfDifferent(resultPoly, QPointF(x, y));
		}

		QLineF edge(p1, p2);
		QPointF intersectPoint;
		if (line.intersect(edge, &intersectPoint) == QLineF::BoundedIntersection) {
			//resultPoly << intersectPoint;
			AppendPointIfDifferent(resultPoly, intersectPoint);
		}
	}
	return resultPoly;
}