Saving rotated QImage

[Hensim]

Hi There,

I have a Problem saving rotated QImages. I load an Image, rotate it by some angle and want to save the result.
Unfortunately the results look very strange, either black or black & white patterns. (for 90° it works)

Even when i rotate the image and cut out a rectangular part, saving this smaller part has the same problems.

I somehow could not find any related problems.

[Hensim]

maybe i should post my code :)

@
QTransform trans;
trans.rotate(45);
QImage pic = m_currentImage.transformed(trans,Qt::SmoothTransformation);

// n18 is a point in the original image, so i map it with trans and calculate borders of the rect used // later
QPoint tl = (trans.map(n18.toPoint()) - QPoint(75,150));
QPoint br = (trans.map(n18.toPoint()) + QPoint(75,150));

QRect rec = QRect(tl,br);
// this would cut out the rectangle, it also shows in my program as a perfect rectangle
// pic = pic.copy(rec);

QImageWriter w(QCoreApplication::applicationDirPath() + "/imagedat/blub.png","png");
w.write(pic);@

And the output picture does not look any familiar with the original image. Just totally weird.
If i set the angle to 90° it outputs the right picture rotated by 90°.

[Hensim]

If anyone is interested in the Solution:

I now tried to apply the transformation to the pixmap and converted back to QImage and this works!!!

I still wonder why exactly this is the case.