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c++qtqpainterqtgui

Non-elegant chipped ellipses with QPainter

I am drawing an ellipse around a target. However the ellipses are not joined and elegant. By elegant I mean they are not smooth. this is what the ellipse around the image looks like

Notice the circle is not smooth and has roughness I would like to make it a smooth circle/ellipse. Any suggestions on how I could do that ? This is currently how I am doing the ellipses.

QPainter painter(target);

QPen pen;
pen.setColor(Qt::red);
pen.setWidth(4);
pen.setStyle( Qt::SolidLine);
pen.setCapStyle(Qt::SquareCap);
pen.setJoinStyle(Qt::BevelJoin);
painter.setPen(pen);

QRegion r(QRect(0, 0, 50, 50), QRegion::Ellipse); 
painter.setClipRegion(r);
painter.drawPixmap(0, 0, source);
painter.drawEllipse(QRect(1, 1, 49, 49));
Solution

  • You need to enable antialiasing:

    painter.setRenderHint(QPainter::Antialiasing);