Hello,

I create a QPixmap and fill(QPixmap::fill)  it with Qt::transparent. I then 
draw with a QPainter a QImage (with alpha channel/transparency) into it. I then 
set that QPixmap in QGraphicsPixmapItem.

However "visual noise" (stripes, random pixels, garbage, ...) appears in the 
areas which should be fully transparent, as if they weren't initialised.

The same happens with both the "native" and "raster" (even more garbage) paint 
engine with Qt 4.8.2 on OS X 10.8 Mountain Lion (haven't tried Snow Leopard 
10.6 yet...).

The workaround is to fill a QImage first, paint everything in there and then 
convert that into the final QPixmap, but I thought I could save that step.


Anyone else observed this? Am I not supposed to fill a QPixmap with 
Qt::transparent? Is painting into a QImage (including costly conversion to 
QPixmap afterwards) the preferred way anyway?

  Cheers, Oliver


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