在QT中繪製化妝品填充橢圓

Question

我想在QT中繪製一個填充橢圓，在放大和縮小時不會改變其大小。現在我有以下幾點：

QPen pen = painter->pen(); 
pen.setCosmetic(true); 
pen.setWidth(5); 
painter->setPen(pen); 
QBrush brush = painter->brush(); 
brush.setStyle(Qt::SolidPattern); 
painter->setBrush(brush); 
painter->drawEllipse(p, 2, 2); 

當我縮小邊界和填充之間的差距出現。所以它看起來像2個同心圓。當我放大填充物時，邊界越來越大，磁盤越來越大。任何想法如何解決這個問題？謝謝！

Answer 1

我反而會看ItemIgnoresTransformations flag，這將使物品本身「美觀」，而不僅僅是筆。這是一個工作示例：

#include <QtGui> 

class NonScalingItem : public QGraphicsItem 
{ 
public: 
    NonScalingItem() 
    { setFlag(ItemIgnoresTransformations, true); } 

    QRectF boundingRect() const 
    { return QRectF(-5, -5, 10, 10); } 

    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) 
    { 
     QPen pen = painter->pen(); 
     pen.setCosmetic(true); 
     pen.setWidth(5); 
     pen.setColor(QColor(Qt::red)); 
     painter->setPen(pen); 
     QBrush brush = painter->brush(); 
     brush.setStyle(Qt::SolidPattern); 
     painter->setBrush(brush); 
     painter->drawEllipse(QPointF(0, 0), 10, 10); 
    } 
}; 

int main(int argc, char *argv[]) 
{ 
    QApplication app(argc, argv); 

    QGraphicsScene *scene = new QGraphicsScene; 
    QGraphicsView *view = new QGraphicsView; 
    NonScalingItem *item = new NonScalingItem; 

    scene->addItem(item); 
    view->setScene(scene); 

    /* The item will remain unchanged regardless of whether 
     or not you comment out the following line: */ 
    view->scale(2000, 2000); 

    view->show(); 
    return app.exec(); 
}