Can you provide a minimal compilable example that reproduces the problem?

My guess is that you're trying to create very large pixmaps (larger than the screen) which isn't needed and may fail on some systems. It's hard to help more without details.

A QImage an be any size you want (provided there's enough system memory) but a QPixmap is specifically used to display, so it doesn't make sense to have a pixmap larger than the screen typically.