qPixmap retrieve size ( MB/KB ), scalling image performance

[Talei]

As always thank You very much for reply.
Another question is how to determine size of qpixmap after scaling? In example I want to import -> scale -> display size information -> save to file scaled image.

Also I'm using list/table View to display thumbnails so I prescale every Image, I know that I can retrieve information from views about what items are displayed, so I thought that I would scale only Images that are currently displayed and when user scroll automatic scale rest of them. Any suggestion how to proceed with this are more then welcome.