Qt Ellipse Border Thins Out

问题

I am trying to draw an ellipse in Qt and the border on the edges goes thin in some places.

Here is the code:

QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
painter.setPen(QPen(Qt::black, 3));
painter.drawEllipse(event->rect());

Any ideas? Thanks in advance.

回答1:

When painting a shape with an outline, you have to factor in the width of the pen. So in your case, change to this:

// Adjusted by 2 pixels because half your pen width is 1.5, but QRect is
// for integer types, so rounded up.
painter.drawEllipse(event->rect().adjusted( -2, -2, 2, 2 ) );

来源：https://stackoverflow.com/questions/11239964/qt-ellipse-border-thins-out