QGraphicsPixmapItem quality degraded when rotated

dporobic

Does anyone know why a quality of a QGraphicsPixmapItem degrades after rotating it?

This is the original image:

This one is rotated by just 1°:

So far I have tried setting the TransformationMode:

setTransformationMode(Qt::SmoothTransformation);

And painting it manually:

painter->setRenderHints( QPainter::Antialiasing | QPainter::SmoothPixmapTransform );
painter->drawPixmap( boundingRect().topLeft(), myOriginalPixmap );

Without any noticeably change there.

This is how the rotation is done:

auto center = boundingRect().center();
auto transform = this->transform();
transform.translate(center.x(), center.y());
transform.rotate(angel);
transform.translate(-center.x(), -center.y());
setTransform(transform);

I have also tried rotating with this, but the effect was the same:

setRotation(angel);

What I have noticed is that rotating by 90°, 180°, 270° and 360° looks ok.
Any Ideas how to fix this?