我正在尝试自动从折线创建多边形
到目前为止,我一直在正确计算折线每个部分的外推边。
条件 - 基线和边之间的距离是常数。
这是我在 Qt 中的代码。这对我来说很好用
QPolygonF projectPLineToScreenAsPolygon(QPolygonF pline, qreal halfWidth)
{
QPolygonF ret;
QLineF l2_last;
QLineF l4_last;
for(int i = 0; i < pline.size() - 2; i++){
float x1 = pline.at(i).x();
float y1 = pline.at(i).y();
float x2 = pline.at(i + 1).x();
float y2 = pline.at(i + 1).y();
float x3 = pline.at(i + 2).x();
float y3 = pline.at(i + 2).y();
float dist = sqrt(((x1-x2)*(x1-x2))+((y1-y2)*(y1-y2)));
float dist2 = sqrt(((x3-x2)*(x3-x2))+((y3-y2)*(y3-y2)));
QLineF l1;
QLineF l2;
QLineF l3;
QLineF l4;
if(i > 0){
l1 = l2_last;
l3 = l4_last;
l2 = QLineF (QPointF(x2 + halfWidth * (y3 - y2) / dist2, y2 + halfWidth * (x2 - x3) / dist2), QPointF(x3 + halfWidth * (y3 - y2) / dist2, y3 + halfWidth * (x2 - x3) / dist2));
l4 = QLineF (QPointF(x2 - halfWidth * (y3 - y2) / dist2, y2 - halfWidth * (x2 - x3) / dist2), QPointF(x3 - halfWidth * (y3 - y2) / dist2, y3 - halfWidth * (x2 - x3) / dist2));
} else {
l2 = QLineF (QPointF(x2 + halfWidth * (y3 - y2) / dist2, y2 + halfWidth * (x2 - x3) / dist2), QPointF(x3 + halfWidth * (y3 - y2) / dist2, y3 + halfWidth * (x2 - x3) / dist2));
l4 = QLineF (QPointF(x2 - halfWidth * (y3 - y2) / dist2, y2 - halfWidth * (x2 - x3) / dist2), QPointF(x3 - halfWidth * (y3 - y2) / dist2, y3 - halfWidth * (x2 - x3) / dist2));
l1 = QLineF (QPointF(x1 + halfWidth * (y2 - y1) / dist, y1 + halfWidth * (x1 - x2) / dist), QPointF(x2 + halfWidth * (y2 - y1) / dist, y2 + halfWidth * (x1 - x2) / dist));
l3 = QLineF (QPointF(x1 - halfWidth * (y2 - y1) / dist, y1 - halfWidth * (x1 - x2) / dist), QPointF(x2 - halfWidth * (y2 - y1) / dist, y2 - halfWidth * (x1 - x2) / dist));
}
l2_last = l2;
l4_last = l4;
QPointF pi1;
if(i == 0){
ret.append(l1.p1());
ret.prepend(l3.p1());
}
if(l1.intersect(l2, &pi1) != QLineF::NoIntersection){
ret.append(pi1);
} else {
ret.append(l2.p1());
}
QPointF pi2;
if(l3.intersect(l4, &pi2) != QLineF::NoIntersection){
ret.prepend(pi2);
} else {
ret.prepend(l4.p1());
}
if(i == pline.size() - 3){
ret.append(l2.p2());
ret.append(l4.p2());
}
}
return ret;
}
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